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Acute shortage of water resources and high unproductive water losses are the key problems of irrigated agriculture in arid regions. One of the possible solutions is to optimize soil water retention using natural and synthetic polymer water absorbers. Our approach uses the HYDRUS-1D design to optimize the placement of organic water absorbents such as peat and composite hydrogels in the soil profile in the form of water-storing capillary barriers. Field testing of the approach used a water balance greenhouse experiment with the cultivation of butternut squash (butternut squash (Cucurbita moschata (Duchesne, 1786)) under sprinkler irrigation with measurement of the soil moisture profile and unproductive water losses in the form of lysimetric water outflow. In addition, the biodegradation rate of organic water absorbents was studied at the soil surface and at a depth of 20 cm. Organic capillary barriers reduced unproductive water losses by 40–70%, retaining water in the topsoil and increasing evapotranspiration by 70–130% with a corresponding increase in plant biomass and fruit yield. The deepening of organic soil modifiers to the calculated depth not only allowed capillary barriers to form, but also prevented their biodegradation. The best results in soil water retention, plant growth and yield according to the "dose-effect" criterion were obtained for a composite superabsorbent with peat filling of an acrylic polymer matrix. The study showed good compliance between the HYDRUS design and the actual efficiency of capillary barriers as an innovative technology for irrigated agriculture using natural and synthetic water absorbents. [ABSTRACT FROM AUTHOR]

Soil surface cover is one of the most critical factors affecting soil water vapor transport, especially in drylands where water is limited, and the water movement occurs predominantly in the form of vapor instead of liquid. Biocrusts are an important living ground cover of dryland soils and play a vital role in modifying near‐surface soil properties and maintaining soil structure. The role of biocrusts in mediating soil water vapor transport during daytime water evaporation and nighttime condensation remains unclear. We investigated the differences in vapor diffusion properties, vapor adsorption capacity, and water evaporation between bare soil and three types of biocrusts (cyanobacterial, cyanobacterial‐moss mixed, and moss crusts) in the Chinese Loess Plateau. Our results showed that the three types of biocrusts had 5%–39% higher vapor diffusivity than bare soil. At the same level of ambient relative humidity and temperature, the initial vapor adsorption rates and cumulative adsorption amounts of the biocrusts were 10%–70% and 11%–85% higher than those of bare soil, respectively. Additionally, the late‐stage evaporation rate of cyanobacterial‐, cyanobacterial‐moss mixed‐, and moss‐biocrusts were 31%–217%, 79%–492%, and 146%–775% higher than that of bare soil, respectively. The effect of biocrusts on increasing vapor transport properties was attributed to the higher soil porosity, clay content, and specific surface area induced by the biocrust layer. All of these modifications caused by biocrusts on surface soil vapor transport properties suggest that biocrusts play a vital role in reshaping surface soil water and energy balance in drylands. Key Points: Biocrusts increase water vapor diffusion properties, water vapor adsorption amount, and cumulative evaporation amountModified soil properties of biocrust are a key factor influencing water vapor fluxReshaped vapor transport properties of biocrust control soil water and energy balance [ABSTRACT FROM AUTHOR]

AbstractThe experiment was conducted to determine the irrigation scheduling effect on hot pepper green pods, yield attributes, and irrigation water productivity (WP) in the Arba Minch area. Field trials comprised five levels of treatments: 140 % MAD, 120% MAD, 100% MAD, 80% MAD and 60% MAD. The results revealed that different depletion levels had significantly affected hot pepper’s yield and related attributes. The maximum yield of hot pepper was observed under 100% MAD without significant variation of 120% MAD whereas the minimum was under 140% MAD in both years of experimentation. WP was also highly influenced by depletion, and the maximum water productivity of (24.67 kg/ha-mm, 24.72 kg/ha-mm was observed under 120% MAD and minimum (19.26 kg/ha-mm, 16.49 kg/ha-mm) under 60% MAD in the year 2019 and 2021, respectively. The results revealed that as the level of depletion increased, irrigation frequency (event) increased, yield and water productivity decreased of hot peppers. 120% MAD offered the highest economic return (11,795.96 US$) and saved water, wage, and irrigation events compared to more frequent applications. The current findings showed that applying 120% MAD is better for hot pepper production in the Arba Minch areas and similar ecology.

Hydropedology is an interdisciplinary field that studies the interactions between soil and water, recognizing that soils influence hydrological processes through their hydraulic properties, and serve as indicators of hydrological behaviour through their morphological properties that are shaped by water regimes. Given the practical implications of hydropedology and its integration into South Africa's latest soil classification system, an updated categorization of soil forms and 1 657 (1 629 + 28) families was necessary, organizing them into three overarching response groups based on their predominant hydrological responses: recharge, interflow, and responsive. Within these groups, recharge soils are further classified into deep, shallow, and slow subgroups, interflow soils encompass soil/bedrock, shallow, and slow categories, while responsive soils are subdivided into responsive shallow and responsive wet. This paper aims to enhance the reader's comprehension of hydrological responses and simplify the intricacies integrated into South Africa's official soil classification system. [ABSTRACT FROM AUTHOR]

The present study is conducted in the Upper Mille River catchment of the Lower Awash Basin in Ethiopia. The main aim of the study is to investigate the groundwater potential of a complex fractured volcanic and unconsolidated Quaternary sediment aquifer system using integrated hydrogeological approaches. To estimate the hydrological components of the catchment, the soil water balance (SWB) method and Soil and Water Assessment Tool (SWAT) modeling techniques are employed. The SWB method and the SWAT model indicate that the long-term average annual groundwater recharge of the catchment is 105 mm and 150 mm, respectively, which accounts for 9.3% and 13.8% of the mean annual precipitation. Conventional hydrogeological investigation techniques are used to evaluate the spatial variability and flow dynamics of the groundwater system, as well as the various natures of the aquifers. Based on aquifer productivity, hydraulic conductivity, transmissivity, and discharge values, the aquifer system is classified into three different hydrogeological units: a highly productive intergranular aquifer, a medium productive fractured aquifer, and a low-productive aquifer. Lithological logs of deep boreholes, pumping test results, stratigraphic settings, water balance components, and the topographic position of each unit are also used to classify the aquifers. Schematic hydrogeological cross-sections, total dissolved solid (TDS) and electrical conductivity (EC) distribution maps, and groundwater head distribution contour maps are produced using lithological logs of drilled deep boreholes, field-measured inventory water points, and water level measurements, respectively. Based on converging evidence from geological, hydrogeological, and topographic settings, a conceptual model that approximates the groundwater system of the Upper Mille River catchment is developed, and the groundwater potential of the catchment is evaluated. [ABSTRACT FROM AUTHOR]

This paper highlights the evolution and impact of the SWAP model (Soil – Water – Atmosphere – Plant), which was initiated by R.A. Feddes and colleagues fifty years ago, in 1974. Since then, the SWAP model has played a crucial role in the advancement of agrohydrology. This paper highlights some major advances that have been made, especially focussing on the last fifteen years. The domain of the SWAP model deals with the simulation of the soil water balance in both unsaturated and saturated conditions. The model solves the Richards equation using the water retention and hydraulic conductivity functions as described by the Van Genuchten – Mualem equations. Bimodal extensions of the Van Genuchten - Mualem relationships have been implemented, as well as modifications near saturation and addressing hysteresis. An important sink term in the Richards equation is root water uptake. Crop development plays an important role in a robust simulation of root water uptake. That is why a link has been made with the dynamic crop growth model WOFOST. Instead of using a prescribed crop development, a distinction between potential and actual crop development is calculated by reducing the potential photosynthesis as a result of water or oxygen stress. Since the early days of SWAP, empirical and macroscopic concepts have been used to simulate root water uptake. Recently two process-based concepts of root water uptake and oxygen stress have also been implemented. Another important sink-source term in the Richards equation is the interaction with artificial drains. In SWAP, drainage can be simulated by either using prescribed or simulated drain heads and simulation of controlled drainage with subirrigation is possible. Finally, we briefly elaborate on three studies using SWAP: water stresses in agriculture in the Netherlands, regional water productivity in China, and controlled drainage with subirrigation. We finish discussing promising developments for the near future.

A national web-based simulation portal was developed to estimate the irrigation water requirements at plain scale in Iran. The National Water Portal (NWP) consists of four national databases (climatic, soil, crop, and spatial data), a lumped water balance model, and a graphical user interface (GUI). The irrigation water requirements in standard conditions were estimated based on the dual crop coefficient approach presented by FAO 56. Net irrigation requirements (NIR) and gross irrigation requirements (GIR) were calculated for 125 different crops cultivated in the 609 plains in Iran. Results were aggregated at both political and hydrological scales. The statistical comparison between the estimated NIR and reported values in the literature reviews indicates a correlation coefficient of 75% with root mean square error (RMSE) of less than 280 m3 ha−1. Results showed that sugar cane has the highest NIR value (18318 m3 ha−1) among the studied crops, and sugar beet has the second highest NIR value (5100–11896 m3 ha−1). The aggregated amount of NIR and GIR for the entire country was calculated as 47 and 105 billion cubic meters (BCM), respectively. Results indicate that 3.772 million cubic meter (MCM) of water can be saved by applying 15% water stress. By increasing the irrigation efficiency to 65% without considering any water stress, 3.482 MCM of water can be saved.

Acute shortage of water resources and high unproductive water losses are the key problems of irrigated agriculture in arid regions. One of the possible solutions is to optimize soil water retention using natural and synthetic polymer water absorbers. Our approach uses the HYDRUS-1D design to optimize the placement of organic water absorbents such as peat and composite hydrogels in the soil profile in the form of water-storing capillary barriers. Field testing of the approach used a water balance greenhouse experiment with the cultivation of butternut squash (butternut squash (Cucurbita moschata (Duchesne, 1786)) under sprinkler irrigation with measurement of the soil moisture profile and unproductive water losses in the form of lysimetric water outflow. In addition, the biodegradation rate of organic water absorbents was studied at the soil surface and at a depth of 20 cm. Organic capillary barriers reduced unproductive water losses by 40–70%, retaining water in the topsoil and increasing evapotranspiration by 70–130% with a corresponding increase in plant biomass and fruit yield. The deepening of organic soil modifiers to the calculated depth not only allowed capillary barriers to form, but also prevented their biodegradation. The best results in soil water retention, plant growth and yield according to the “dose-effect” criterion were obtained for a composite superabsorbent with peat filling of an acrylic polymer matrix. The study showed good compliance between the HYDRUS design and the actual efficiency of capillary barriers as an innovative technology for irrigated agriculture using natural and synthetic water absorbents.

An accurate assessment of crop water requirements during the crop growth period can help organize irrigation schedules and investigate the hydrological environments in irrigation districts, especially in shallow groundwater districts. In irrigation scheduling, crop coefficients, representing three development stages, play a critical role in modeling evapotranspiration. Therefore, in this study, the crop coefficient (Kc) of sunflowers under drip irrigation in different hydrological years in the Hetao irrigation district with shallow groundwater is determined. Based on the analysis of rainfall frequency, the experimental situations of 2012, 2013, and 2014 are adopted as high, normal, and low flow years. Using the water balance method, groundwater recharge and crop evapotranspiration in different hydrological years were investigated. The results showed that the groundwater recharge in a high-flow year was larger than that in normal and low-flow years with values of 67.47, 66.75, and 42.61 mm, respectively. Crop evapotranspiration is directly related to the irrigation amount at the same growth stage. The Kc of sunflowers in a high-flow year is higher by 0.1 and 0.15 than that in normal and low-flow years. The Kc of sunflowers under drip irrigation is lower than that under surface irrigation by 8.9% in the initial and late stages of sunflower growth, but higher than that by 10.6% in the mid-stage, which is due to differences in small water potential differences and less evapotranspiration in the initial and late stages under drip irrigation. The study is of great significance for formulating a reasonable schedule of drip irrigation with shallow groundwater and improving the field environment. [ABSTRACT FROM AUTHOR]

A national web-based simulation portal was developed to estimate the irrigation water requirements at plain scale in Iran. The National Water Portal (NWP) consists of four national databases (climatic, soil, crop, and spatial data), a lumped water balance model, and a graphical user interface (GUI). The irrigation water requirements in standard conditions were estimated based on the dual crop coefficient approach presented by FAO 56. Net irrigation requirements (NIR) and gross irrigation requirements (GIR) were calculated for 125 different crops cultivated in the 609 plains in Iran. Results were aggregated at both political and hydrological scales. The statistical comparison between the estimated NIR and reported values in the literature reviews indicates a correlation coefficient of 75% with root mean square error (RMSE) of less than 280 m3 ha-1. Results showed that sugar cane has the highest NIR value (18318 m3 ha-1) among the studied crops, and sugar beet has the second highest NIR value (5100-11896 m3 ha-1). The aggregated amount of NIR and GIR for the entire country was calculated as 47 and 105 billion cubic meters (BCM), respectively. Results indicate that 3.772 million cubic meter (MCM) of water can be saved by applying 15% water stress. By increasing the irrigation efficiency to 65% without considering any water stress, 3.482 MCM of water can be saved. [ABSTRACT FROM AUTHOR]

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Straw mulching incorporation has a wide range of environmental benefits that make it an effective practice for sustainable agro-ecosystem in the semi-arid regions. There is an urgent need to improve the 13C-photosynthates distribution, water use efficiency (WUE) and maize canopy characteristics under the diverse tillage practices with straw mulched management strategies for sustainable intensification of maize production. The field study consists of three diverse tillage systems (RT: rotary tillage; CT, conventional tillage; MT, minimum tillage) with three straws mulching (NS: no straw mulch; SS: straw mulch on the soil surface; SI: straw incorporated into the soil) were assessed under the ridge-furrow rainfall harvesting system. Our results showed that the rotary tillage with straw incorporated into the soil significantly reduces the ET rate (11 %), and leaf rolling index; as a result considerably improves LAI, LEI, 13C-photosynthates distribution, N accumulation, and above ground biomass under various growth stages. The RTSI treatment significantly improved soil water storage, soil organic carbon (52 %, SOC), soil C storage (39 %, SCS), and NPK nutrients uptake (70 %, 62 %, and 69 %) of maize than observed for the rest of all other treatments, respectively. The RTSI treatment improves soil water balance, grain yield (53 %), biomass yield (37 %), WUEg (51 %), WUEb (35 %), nutrients uptake, and mitigating soil water depletion than the MTNS treatment. Although RTSS can achieve optimal soil water storage in the short term, RTSI has a great potential in improving soil carbon stability, canopy characteristics, soil water storage, and WUE, contributing to sustainable and intensive corn production in agricultural ecosystems in semi-arid regions.

Accurate estimation of crop evapotranspiration (ETc) and soil water balance, which is vital for optimizing water management strategy in crop production, can be performed by simulation. But existing software has many deficiencies, including complex operation, limited scalability, lack of batch processing, and a single ETc model. Here we present simET, an open-source software package written in the R programming language. Many concepts involved in crop ETc simulation are condensed into functions in the package. It includes three widely used crop ETc models built on these functions: the single-crop coefficient, double-crop coefficient, and Shuttleworth–Wallace models, along with tools for preparing model data and comparing estimates. SimET supports ETc simulation in crops with repeated growth cycles such as alfalfa, a perennial forage crop that is cut multiple times annually.

The agricultural sector is facing a pressing need to adopt variable-rate irrigation decision support systems (VRI–DSS) to address global challenges such as water quality, water scarcity, food security, and climate change. This study evaluated a model-based VRI–DSS for maize and sweetcorn crops in a commercial field with two soil zones and a VRI center pivot. The evaluation involved assessing the farmer’s use of the system and comparing the VRI–DSS outputs using default parameters (e.g. virtual climate data) with outputs using local data. The results showed good agreement between the virtual and local climate data (R2 = 0.94, RMSE = 0.51 °C for air temperature; R2 = 0.79, RMSE = 0.53 mm/day for evapotranspiration), except for rainfall, which was overestimated by 12% by the VRI–DSS. The soil water deficit estimates from the local data also matched well with the neutron probe measurements. The farmer applied less irrigation due to water restrictions, but water use efficiency varied between soil zones for sweetcorn. The evaluation showed that VRI–DSS, with accurate climate data, is a useful tool for estimating variable-irrigation requirements for maize and sweetcorn under one system. However, more field data and local rainfall data are required to validate the decision software system. [ABSTRACT FROM AUTHOR]

A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Knowledge of the soil water balance is fundamental for improving crop water use in agricultural fields. Estimates are normally for representative and homogeneous areas where the variability of soil properties is neglected. However, this variability significantly impacts soil water dynamics at the field scale. In this study, the MOHID-Land distributed process-based model was used to compute the spatially explicit soil water dynamics in a 22.6-ha almond field located in southern Portugal. An electromagnetic induction survey was first performed to obtain electromagnetic images of the real soil conductivity in depth, which were related to soil texture. Then, pedotransfer functions were used to convert soil texture into soil hydraulic data. MOHID-Land results included maps of the spatial distribution of soil water contents, actual crop transpiration, actual soil evaporation, percolation below the rootzone, and surface runoff. These allowed identifying preferential flow pathways as well as the main control factors influencing soil water dynamics at the field scale. Some development needs were identified, and overcoming them would enhance the significance of contributions such as this study to the field of precision agriculture.

The purpose of this study was to evaluate alternative management practices such as in-field rainwater harvesting (IRWH) and intercropping techniques through conducting on-farm demonstrations. Seven homestead gardens in Thaba Nchu rural communities in the central part of South Africa were selected as demonstration trials. Two tillage systems, conventional (CON) and IRWH, as the main plot, and three cropping systems as sub-plot (sole maize and beans and intercropping) were used to measure water use and radiation use parameters. The water productivity (WP) of various treatments was positively related to the radiation use efficiency (RUE), and the degree of associations varied for different tillage systems. The water use in IRWH was higher by 15.1%, 8.3%, and 10.1% over the CON for sole maize and beans and intercropping, respectively. Similarly, the intercropping system showed water use advantages over the solely growing crops by 5% and 8% for maize and by 16% and 12% for beans under IRWH and CON tillage, respectively. Maximum RUE was found for sole maize and beans under IRWH, higher by 13% and 55% compared to the CON tillage, respectively. The RUE under IRWH tillage was estimated to be 0.65 and 0.39 g DM MJ−1 in sole maize and intercropping, respectively. However, in sole and intercropped beans, the RUE showed higher values of 1.02 g DM MJ−1 and 0.73 g DM MJ−1, respectively. WP and RUE were associated with water deficits and proportional to lower radiation use. This relationship indicates that the intercepted radiation by plants for photosynthesis is directly related to the transpiration rate until radiation saturation occurs. Therefore, the higher water deficit and lesser efficiency in using the radiation available during the season can be improved by practicing IRWH techniques. Furthermore, in semi-arid areas, to enhance the efficiency of water and radiation usage in intercropping management, it is crucial to adjust plant population and sowing dates based on water availability and the onset of rainfall. [ABSTRACT FROM AUTHOR]

Nowadays, changes in precipitation patterns together with the increasing water demand impose a sustainable management where the budget between water availability and demand is positively closed. A parsimonious hydrogeological modelling approach coupled with a soil water balance is developed and applied in order to quantify the hydrological and hydrogeological dynamics in a semi-arid region of the Mediterranean basin. In particular, the present work focuses on the hydrogeological dynamics of the catchment areas of Siedi, Foggia di Rau, Pigonati, and the Palmarini channels located in the Brindisi Plain, Southern Italy. In the last decades, in the Brindisi Plain the anthropization processes as well as the industrial and agricultural development have generated an intensive exploitation of both shallow and deep groundwater resources as well as their qualitative deterioration. A dry hydrologic year (2019–2020) caused a recharge deficit, resulting in a lowering of the groundwater level of the shallow aquifer compared to the expected seasonal value. The results evidence a sensitive natural system, where the variability of the rainfall regime combined with water withdrawal leads to a system that is very vulnerable to climate change impacts, such as the presence of erratic rainfall patterns affecting aquifer recharge. This study represents the first approach to couple a soil moisture balance model and groundwater flow model to assess the impact of changes in rainfall patterns on groundwater recharge for the Brindisi Plain aquifer. The developed integrated hydrogeological model can be applied to other sites with similar hydrogeological features and represents an important tool in order to evaluate the effectiveness of cost-effective sustainable actions for the management of the groundwater resources with respect to land-use practices and socio-economic aspects. [ABSTRACT FROM AUTHOR]

[Objective] The aim of this study is to explore the impact of land use change (LUC) on various hydrological variables in soil water balance as well as the mechanism of water cycle in loess region, and then to provide technical support for similar research. [Methods] We chose the Changwu loess tableland as the study area, and then collected soil samples from the surface down to 20 m under three land use types (farmland, 18-year apple orchard and 26-year apple orchard). Then, the content of soil water, stable (δ²H and δ18O) and radioactive (³H) isotopes were measured. The components of soil water balance were decomposed and quantified, and their responses to land use changes were evaluated. [Results] Compared with farmland, the soil water storage under apple orchard (stand age 18 and 26 years) decreased by 7.3%～14.3%, the deep drainage decreased by 41.2%～80.0%, and the evapotranspiration increased by 5.0%～9.6%, of which evaporation decreased by 8.6%～17.2%, while transpiration increased by 12.9%～25.4%. [Conclusion] There were significant differences in soil water contents under three land use types, and the soil water oxygen isotope profiles showed a general trend of decreasing and then stabilizing, with soil water subject to the strongest evaporation under farmland. Deep-rooted fruit trees mainly reduced the flux of other hydrological variables by increasing transpiration water consumption, which significantly affected the hydrological process. [ABSTRACT FROM AUTHOR]

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Introduction Water scarcity due to climate change and growing water demand in different consumption sectors is a major environmental crisis that drives arable lands to a state of degradation, especially in dry regions. Artificial recharge of groundwater (ARG) through floodwater spreading (FWS) which is a potential measure for reversing this emerging trend is investigated in this research. Floodwater harvesting has become an increasingly important technique to improve water security and caused a renewed interest in research and implementation. According to the diverse objectives and methods of implementing artificial recharge of groundwater (ARG) systems, various factors must be considered when choosing a method for quantifying recharge. Therefore, the rate of aquifer recharge is one of the most difficult items to measure in groundwater (GW) resources evaluation. In the soil water balance method (and in the Zero Flux Plane method), soil water movement is inferred by measuring the changes in water content of the soil profile by gravimetric sampling or automatic devices. These methods have not been proven satisfactory in low flow conditions, as there is often insufficient resolution to detect the movement of small quantities of water. Therefore, other methods, based on hydraulic conductivity, potential gradients, and directly calculated water fluxes for unsaturated flow were developed. The Buckingham-Darcy law can be used under the steady flow condition where water contents and fluxes change with depth but do not vary as a function of time. It has been employed in arid and semiarid conditions for recharge estimation. or for assessing the exchange flow between the surface water reservoir and GW. The method requires measurements or estimates of the vertical total head gradient and the unsaturated hydraulic conductivity at the ambient soil water content following the Buckingham-Darcy equation. The overall objective is to evaluate a floodwater spreading system that was installed in 1981 at the Gareh Bygone Plain, southern Iran for recharging the groundwater table. Materials and Methods To assess the artificial recharge of groundwater through turbid floodwater spreading, three wells, ~30 m deep, were dug in a 37-year-old recharge basin in planted Acacia forest, bare soil, and pasture land uses, respectively. Soil hydraulic parameters of the vadose zone layers (30 m thickness) were measured in the field and laboratory. One well was equipped with pre-calibrated TDR sensors throughout the well profile for measuring the changes in soil water content along the vadose zone. The volumetric soil-water content was measured continuously from Sep. 2010 to Sep. 2020 with closer temporal increments after floodwater spreading events. Rainfall, ponding water depth, and duration were also measured. Recharge through the vadose zone was assessed by the soil-water balance (SWB) method, as measured in the field as well as by calibrating the Hydrus-1D (H1D) model through the inverse solution. Results and discussion Results showed that the wetting front was interrupted at a layer with fine soil accumulation over a coarse-textured gravely layer at a depth of ~4 m. The large differences in hydraulic conductivity of the two successive layers seemed to cause the transformation of the wetting front water movement into fingering flow. The changes in downward water flux complicated TDR measurement after the depth of 4 m. However, noticeable but temporary changes in the soil water content were detected in some of the layers below the 4 m was evidence for fingering flow after the flood events. Validation of the simulated flow by the H1D model vs. the one observed by SWB (with RMSE 3.45; R2 0.994) showed that the model performed well in flux estimation. The recharge ratio was calculated for the 2010 to 2020 events as 26 to 84 average of 55 % for all events and 63 to 84 average of 75 % for large impounded floodwater in the basin, respectively. Conclusion Although a reliable set of data is obtained for calculating recharge at the very location of this study, up-scaling of the results for the entire floodwater systems and for the other flooding events with extreme volume and flow rate needs an extended investigation period and thorough identification of the underlying layers. The determined hydraulic properties of the RLs obtained in this study will be utilized in future research works in the FWS systems in our study site. The contributions of this thesis can be summarized as a) development of approaches for application, calibration, and validation of existing models with limited available data, b) the incorporation of new concepts into the models used, c) generating a unique and robust field data set to support the modeling approaches and d) provision of new information in the context of floodwater harvesting and its impact on groundwater recharge. Floodwater harvesting, especially in the form of FWS, is an emerging issue in water management in dry regions, which needs a better understanding and evaluation of its impact on the surrounding environment. Small-scale but nature-friendly water management plans, such as FWS systems, are seriously criticized since there are numerous methods, which are more attractive in terms of investments and money return to investors. However, they are rarely investigated. This study provided quantitative evidence that proves the effectiveness of FWS systems.

Estimating potential recharge is essential to water resource management, urban/agricultural development planning, and the definition of pumping rates to prevent or mitigate aquifer overexploitation. In the Toluca Valley, high extraction rates have induced piezometric declines accompanied by a water imbalance exceeding the average annual recharge volume. In this study, a daily soil moisture balance was developed for estimating historical and future potential recharge. The analysis period includes 1980 to 2021 and a projection until 2050 based on three probable scenarios of precipitation, temperature, and urban growth. The results indicate an average annual recharge volume of 369.5 Mm3 with a 174.5 mm/year rate, reaching 355.7 mm/year in wet seasons. The spatial distribution suggests a recharge conditioned in the mountainous areas mainly by the climatology and in the center of the Valley by the land use modification. Urban sprawl is a significant factor in increased runoff and the gradual decrease in interception and actual evapotranspiration. The decrease in recharge is a constant in the potential future recharge scenarios. Compared to the historical average, a negative change of 16.59%, 19.99%, and 22.61% is projected for the best, moderate, and bad scenarios, respectively. The potential recharge rates obtained are an initial parameter in regional basin flow models and analyses. [ABSTRACT FROM AUTHOR]

The climate of Southeastern Europe, where Bosnia and Herzegovina (BiH) and Croatia are located, is changing in line with the global trends. The spatial and seasonal distribution of precipitation is changing, while the temperatures increased 0.4-0.8 oC on average compared to 1961-1990, most notably during summer (1.0-1.2 oC). Depending on the different Representative Concentration Pathway (RCP) scenarios, the temperatures in this area are projected to further increase by 1.7-4.0 °C. In order to understand the effects of climate change on regional water resources, it is important to assess the impacts of these changes on the components of the water balance. The aim of this study was to determine and compare the severity of changes in annual water balance between two climate periods (1961-1990 and 1991-2020). The results indicate that climate change has a different temporal and spatial effect. All areas showed a positive trend in mean air temperature (0.29-0.36 oC per decade), reference evapotranspiration (5.96-32.14 mm per decade) while precipitation, total runoff, amount of snow and actual evapotranspiration vary depending on the location and time period. The key characteristic of the 1991-2020 period compared to 1961-1990 is the greater variation of all components of the water balance. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is critical for ecosystem protection and water services, especially in the mountainous areas of arid and semi-arid watersheds. The lysimeter and Eddy Covariance (EC) methods are widely used for directly measuring ET, but are difficult to install and apply in mountainous areas with complex topography. The commonly used indirect methods for estimating ET, such as the Penman-Monteith (PM) method, present significant challenges in mountainous areas with scarce data. The simple soil water balance (SWB) method, which estimates ET from soil moisture dynamics, is another reliable and simple method for estimating ET. However, a drawback of the original SWB method is that it assumes soil moisture depletion only occurs through ET, ignoring the process of deep percolation. This restriction limits the applicability of the SWB method. In this study, we improve the SWB method (ISWB) by incorporating a deep percolation module into the soil water balance equation. Subsequently, we compare the estimated ET obtained from the ISWB, the Food and Agriculture Organization (FAO)-56 PM, and the Hargreaves-Samani (HS) methods with the observed ET. Results show that the ISWB method for estimating ET performs better when using the soil moisture of the 0–25 cm and below layers, compared to the 0–20 cm and above layers. Meanwhile, there is no significant difference in performance between using the soil moisture of the 0–25 cm layer and the soil layers below 25 cm. In addition, ignoring interception evaporation has an obvious influence on ET estimation using the ISWB. Furthermore, the comparison indicated that the performance of the ISWB method is superior to that of the FAO-56 PM and HS methods in the study areas. Our study shows that the ISWB method has significant potential for ET estimation in data-scarce and topographic-complex mountainous areas.

An accurate assessment of crop water requirements during the crop growth period can help organize irrigation schedules and investigate the hydrological environments in irrigation districts, especially in shallow groundwater districts. In irrigation scheduling, crop coefficients, representing three development stages, play a critical role in modeling evapotranspiration. Therefore, in this study, the crop coefficient (Kc) of sunflowers under drip irrigation in different hydrological years in the Hetao irrigation district with shallow groundwater is determined. Based on the analysis of rainfall frequency, the experimental situations of 2012, 2013, and 2014 are adopted as high, normal, and low flow years. Using the water balance method, groundwater recharge and crop evapotranspiration in different hydrological years were investigated. The results showed that the groundwater recharge in a high-flow year was larger than that in normal and low-flow years with values of 67.47, 66.75, and 42.61 mm, respectively. Crop evapotranspiration is directly related to the irrigation amount at the same growth stage. The Kc of sunflowers in a high-flow year is higher by 0.1 and 0.15 than that in normal and low-flow years. The Kc of sunflowers under drip irrigation is lower than that under surface irrigation by 8.9% in the initial and late stages of sunflower growth, but higher than that by 10.6% in the mid-stage, which is due to differences in small water potential differences and less evapotranspiration in the initial and late stages under drip irrigation. The study is of great significance for formulating a reasonable schedule of drip irrigation with shallow groundwater and improving the field environment.

This note makes available five years of data gathered in a measurement site equipped with a micrometeorological station and two monitoring wells. Series of data of hydrological and atmospheric variables make it possible to estimate the flux of water across the atmosphere-land interface and to calculate the water budget, which are crucial topics in climate and environmental sciences. The water-table measures began during 2017, one of the driest years of the whole instrumental period of climate history for the Central Mediterranean. Data from the micrometeorological station have been used to construct two more datasets of daily and monthly totals of different terms of the surface water budget, from which the net infiltration has been estimated. An apparent decreasing trend characterizes both the data time series of groundwater level and estimated infiltration in the considered period. Data Set: The datasets are stored on the Zenodo repository: https://doi.org/10.5281/zenodo.7572140. Data Set License: CC-BY 4.0 [ABSTRACT FROM AUTHOR]

Nowadays, smart irrigation is becoming an essential goal in agriculture, where water and energy are increasingly limited resources. Its importance will grow in the coming years in the agricultural sector where the optimal use of resources and environmental sustainability are becoming more important every day. However, implementing smart irrigation is not an easy task for most farmers since it is based on knowledge of the different processes and factors that determine the crop water requirements. Thanks to technological developments, it is possible to design new tools such as sensors or platforms that can be connected to soil-water-plant-atmosphere models to assist in the optimization and automation of irrigation. In this work, a low-cost, open-source IoT system for smart irrigation has been developed that can be easily integrated with other platforms and supports a large number of sensors. The platform uses the FIWARE framework together with customized components and can be deployed using edge computing and/or cloud computing systems. To improve decision-making, the platform integrates an irrigation model that calculates soil water balance and wet bulb dimensions to determine the best irrigation strategy for drip irrigation systems. In addition, an energy efficient open-source datalogger has been designed. The datalogger supports a wide range of communications and is compatible with analog sensors, SDI-12 and RS-485 protocols. The IoT system has been deployed on an olive farm and has been in operation for one irrigation season. Based on the results obtained, advantages of using these technologies over traditional methods are discussed. [ABSTRACT FROM AUTHOR]

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• Identify PTFs for all soil hydraulic parameters applicable to the Loess Plateau. • Explore the response of soil erosion to climate change in time and space. • Identify periods and regions at risk for soil moisture regimes under climate change. • Searching for safe and weak zones for future vegetation net primary productivity. Climate change is exacerbating the risk of soil water stress, soil erosion and ecological degradation in the Loess Plateau (CLP). However, the spatiotemporal dynamics of ecohydrological processes, including soil water balance (SWB), soil erosion (SE) and vegetation net primary productivity (NPP), in response to climate change remain isolated and ambiguous. Additionally, existing studies often rely on limited measured data from specific watersheds with particular land use/cover types to establish the pedotransfer functions (PTFs) for single soil hydraulic parameter (SHP). There is a notable lack of comprehensive studies that explore PTFs encompassing all SHPs applicable to the entire CLP, predict the spatiotemporal response of ecohydrological processes to climate change, and identify future risk periods and regions for SWB, SE, and NPP. To address these gaps, we first screened the PTFs applicable for the whole CLP, and then projected the spatiotemporal dynamics of ecohydrological processes from 2020 to 2030 under CMIP6 scenarios by integrating the PTFs with the OpenKarHydro, RUSLE, and CASA model, and finally classified the soil water content, SE and NPP to identify their risk periods and regions. The results showed that the PTFs achieved satisfactory accuracy, with RMSEs for Ks , θs , θr , α , n , θfc and θw being 2.682, 0.109, 0.016, 0.111, 0.897, 0.060 and 0.058, BIASs of 1.365, 0.182, 0.012, 0.031, 0.214, 0.057 and 0.048, R2 s of 0.445, 0.500, 0.430, 0.400, 0.694, 0.453 and 0.453, and NSEs of 0.645, 0.737, 0.874, 0.349, 0.567, 0.756 and 0.458, respectively. SE decreased significantly from 2020 to 2030, with an average annual rate of −6.18 %. Soil water storage decreased significantly between 2020 and 2030, and declining from southeast to northwest. The proportion of area in the wet zone decreased by 4 %, while the proportion of area in the dry zone increased by 11.9 % from 2020 to 2030. The average NPP in 2020–2030 is 320.07 gC·m−2·a−1, with the largest in summer and smallest in winter, and decreasing from southeast to northwest. The NPP increased significantly in 2020–2030, with average annual value and rate of 19.61 gC·m−2·a−1 and 70.84 %, respectively. The NPP increased significantly in spring, summer and autumn, but remained stable in winter. This investigation bridges the gap between existing soil properties, missing SHPs, the strong regional applicability of PTFs, and isolated ecohydrological processes. It is promises to provide valuable insights into the response to climate change in the CLP and another water-limited regions. [ABSTRACT FROM AUTHOR]

• The average values of soil properties within textural classes serve as reliable indicators for estimating soil moisture. • The northern region of the semiarid area features soils with higher hydraulic conductivity and lower water retention. • Inverse modeling has proven to be an efficient tool for estimating soil properties. In semiarid regions, sustainably managing the limited available water resources is critical for food, water, and economic security. An important aspect of water management is monitoring, analyzing, and predicting soil moisture and hydrologic fluxes, especially under the threats of climate change. Unfortunately, since monitoring of soil moisture and water fluxes is often sparse in these regions, one needs to rely on hydrological modeling. The latter requires accurate knowledge of soil properties (e.g., texture, porosity, hydraulic conductivity), which in semiarid regions is also complicated by high level of spatial heterogeneity that is not captured by the low density of soil sampling efforts as well as by globally gridded soil databases. Using 300 monitoring sites across the Semiarid region of NE Brazil and a soil moisture model, this study aims to estimate soil properties at the sites through inverse-modeling and then spatially interpolation these properties via geostatistics. Inverse modeling with the Levenberg–Marquardt algorithm accurately captured soil properties across the sites, while clear spatial patterns in these properties allowed us to confidently interpolation them across the region. Comparing our results with a global soil dataset shows that the latter does not capture spatial variability in the region, underlining the need to leverage small scale information. The derived soil property datasets may then particularly be valuable for regional water and ecosystem management applications. [ABSTRACT FROM AUTHOR]

As a crucial living feature inhabiting the soil–atmosphere boundary, biocrusts play a vital role in liquid water or vapor transport through surface soil and thus have strong effects on soil water regimes. However, it remains unclear how biocrusts affect annual or multiyear soil water budgets through the regulation of evaporation outputs and non‐rainfall water (NRW) or infiltration inputs. Thus, we used automated microlysimeters to continually investigate the differences in evaporation and NRW rates between moss‐dominated biocrusts and bare soil at 0–5 cm depth for 2 years. The upper 30 cm of soil moisture (θ) and water storage (W) of bare soil and biocrusts were also monitored. Our results showed that the daily evaporation rate (E) of biocrusts was 17% higher than bare soil. Especially after rainfall events, biocrusts had higher E and larger cumulative evaporation than bare soil. Besides, the daily NRW of biocrusts averaged 15% higher than bare soil over 2 years. Furthermore, biocrusts increased θ by 11%–76% at 0–10 cm depth but decreased θ by 32%–56% at 20–30 cm depth in comparison to bare soil, and they subsequently decreased W by 20% at 0–30 cm depth. Summarized annually, the NRW amount of biocrusts was 19% higher than bare soil, but at the same time, the cumulative evaporation of biocrusts was also 19% higher than bare soil. Finally, biocrusts resulted in more water loss at shallow depth through evaporation and lessened total W throughout 0–30 cm depth of soil. These findings demonstrate that although biocrusts input more NRW into surface soil, these water inputs partially offset their intensified evaporation. Given that all rainfall water infiltrates into the soil in our study system, our findings indicate that biocrusts may have an overall negative effect on soil water balance there, while at the same time increasing water storage and availability of the deeper soil underlying biocrusts. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties (SHPs) are commonly determined in soil samples with replicas. Whether these replicas are taken at a same location to represent a specific point or at several locations to represent a larger area, the results should be merged into a final data set to be used in modeling. For this data set to be representative, standard errors and a correlation matrix must be considered in the merging process. We present a method to perform this merging and give an example using stochastic realizations of van Genuchten-Mualem (VGM) parameters generated by Cholesky decomposition to merge the SHP and associated statistics into a merged parameter set. To do so, we used VGM parameters obtained at sample scale in three replicas from a Brazilian savanna soil through inverse modeling of laboratory evaporation experiments. The effectiveness and representativeness of the proposed methodology were evaluated by observing the frequency distribution of different levels of output, comparing individual and merged sample properties. The outputs include VGM parameters, retention and conductivity characteristics, and water balance components stochastically predicted by a hydrological model. The performed stochastic merging correctly represented the variability of the combined replicas, especially with respect to hydrological model outputs of soil water balance components. Using the mean hydraulic property parameter values to deterministically predict water balance components may yield values that are substantially different from the mean values of stochastic realizations. This suggests that the deterministic prediction using mean parameter values in vadose zone hydrological modeling may result in unrepresentative outputs. In vadose zone hydrological modeling, soil hydraulic property functions (retention and conductivity) need to be parameterized. This is commonly done by laboratory measurements in soil samples. For a single location, it is common to take some replicas. To characterize a larger area like a plot or a soil type, samples may be taken at different locations within the area. The analysis usually results in the mean parameter values of the fitted equation, their standard deviation, and the correlation between parameters. The method presented here allows merging this information of all replicas into a single set of mean, standard deviation, and correlations representing all analyzed samples. Subsequently, this allows a stochastic evaluation of soil water balance components (evapotranspiration, runoff, drainage) for the respective soil under specific climatic and management boundary conditions to be performed. The obtained results show the method to be robust. Additionally, we show that using the mean values of the hydraulic parameters to deterministically predict the water balance components may give very different results than the mean values of the stochastic realizations. [ABSTRACT FROM AUTHOR]

Increasing water and nitrogen use efficiencies (i.e., WUE and NUE) in dryland agroecosystems to maintain high agricultural output with lower environmental costs, such as minimal soil water depletion and nitrate-N residue, are key responsibilities to assure food security for a growing global population. The impact of N rate on soil water balance, soil nitrate N residue, grain yield, WUE, crop N recovery efficiency (REN), agronomic use efficiency of N fertilizer (AE), and net economic return were examined on maize production on the rainfed Loess Plateau during 2011–2018. Field treatments included four N application rates (N0, no N fertilizer applied; N100, 100 kg N ha−1; N200, 200 kg N ha−1; N300, 300 kg N ha−1). Results showed that compared with N0, grain yield increased by 56, 110, and 115% under N100, N200, and N300, respectively, with corresponding improvements in net economic return of 5497, 10,878, and 11,088 RMB ha−1 yr−1, respectively; no significant difference was detected between N200 and N300. Compared to N0, N fertilization significantly increased WUE through improving photosynthetic WUE (i.e., transpiration efficiency), but there was no significant difference between N200 and N300. Compared to N100, the REN was gradually decreased as N rates increased, AE was not significantly changed under N200 and significantly decreased under N300 due to a decreased leaf photosynthetic NUE. Compared to original soil water storage at 0–300 cm soil depths, after seven years of continuous experiments, treatment of N0 enhanced soil water storage by 52 mm and treatment of N100 had no effect on soil water storage, but treatments of N200 and N300 depleted soil water storage by 73 and 109 mm, respectively. Our findings showed that 200 kg N ha−1 improves WUE and NUE with less environmental cost and should be regarded as the economically optimal N rate on the semiarid western Loess Plateau of China for sustainable maize production. [ABSTRACT FROM AUTHOR]

Accurate hydrological modelling to evaluate the impacts of climate and land use change on water resources is pivotal to sustainable management. Soil information is an important input in hydrological models but is often not available at adequate scale with appropriate attributes for direct parameterisation of the models. In this study, conducted in three quaternary catchments in the midlands of KwaZulu-Natal, three different soil information sets were used to configure SWAT+, a revised version of the Soil and Water Assessment Tool (SWAT). The datasets were: (i) the Land Type database (currently the only soil dataset covering the whole of South Africa), (ii) disaggregation of the Land Type database using digital soil mapping techniques (called DSMART), and (iii) a dataset where DSMART were complemented by field observations and interpretations of the hydropedological behaviour of the soils (DSMART+). Simulated streamflow was compared with measured streamflow at three weirs with long-term measurements, and the impact of the soil datasets on water balance simulations was evaluated. In general, the simulations were acceptable when compared to other studies, but could be improved through calibration and including small reservoirs in the model. The DSMART+ dataset yielded more accurate simulations of streamflow in all three catchments with Nash-Sutcliffe efficiencies increasing by between 9% and 67% when compared to the Land Type dataset. The value of the improved soil maps is, however, highlighted through the enhanced spatial detail of streamflow generation mechanisms and water balance components. The internal catchment processes are represented more accurately, and we argue that South Africa needs a detailed hydrological soil map for effective water resource management. [ABSTRACT FROM AUTHOR]

Precise, accurate knowledge of percolation is key to reliable determination of soil water balance and a crop’s water-use efficiency. This work evaluated an approach to estimate the amount of water percolated in the root zone using soil water content (SWC) data measured at different time intervals. The approach was based on the difference of soil water content within and below the effective root zone of banana plants at different time intervals. A drainage lysimeter was used to compare the measured and estimated percolation data. The approach was then used in a banana orchard under drip and micro sprinkler irrigation, with and without the use of mulch. The soil water storage in the banana’s root zone was evaluated within a two-dimensional soil profile with time domain reflectometry (TDR). Mean percolation measured in the lysimeters did not differ from the approach’s estimates using intervals between SWC readings equal to or longer than 6 h from the end of an irrigation event. Percolation estimates under drip and micro sprinkler irrigation in the field, with and without mulch, were consistent with those measured in the lysimeters, considering the 6-h interval of SWC measurements. Percolation was greater under the drip irrigation system with mulch. The amount of water percolated was not influenced by the presence of mulch under the micro sprinkler system.

Peppermint is one of the most important medicinal and industrial crops in the world, which due to the importance of water, it is necessary to determine its water requirements accurately. This study aimed to determine the water requirement, single and dual crop coefficients of Peppermint. For this purpose, 12 water balance drainable lysimeters were applied. Three lysimeters were used to determine grass and three were applied to estimate the evaporation of bare soil. In addition, in the 6 lysimeters, Peppermint was planted in two groups. The plants of group A and group B continued to grow until the end of flowering and appropriate extraction time, and the plants were harvested 3 times after reaching a height of 10-12 cm. The average water requirements of Peppermint for two lysimeters groups A and B were determined to be 646 and 532 mm, respectively. The single and base crop coefficients for lysimeters in group A were determined to be as 0.68, 1.07, 1.31 and 0.3, 0.88, 1.18 for the initial, development and middle growing stages. For lysimeters in group B, the average of single crop coefficients was determined to be 0.85, 0.92 and 0.95 respectively. Calibration and validation of the SIMDualKc model showed the model's capability and accuracy for proper irrigation planning and scheduling.

In vineyards, the under-vine area is managed to control vegetation growth and to reduce the competing effect of growing plants on vines and fruit development. Applied under-vine management methods are the application of herbicides, soil tillage or the growth of spontaneous vegetation or cover crops. These methods affect pedo-climatic conditions differentially as well as the soil biota and have, therefore, consequences on soil functions and ecosystem services. In the presented case study, the effects of five under-vine management methods on the activity of soil hydrolytic enzymes, the soil water content, vine photosynthetic activity, shoot pruning weight, grape yield and quality are investigated in a vineyard in Lower Austria over three consecutive seasons. Thereby, we hypothesise that a permanent under-vine vegetation cover, either mowed or without mowing, supports the soil microbial communities and soil functions in a way to enhance water and nutrients availability for vines which partly compensates for the competition of the growing vegetation. Our results confirm effects on the soil water balance, more specifically, a reduced soil water content in 11 -20 cm soil depths induced by a permanent vegetation cover as compared to herbicide application or soil tillage. Further consequences of permanent vegetation below vines were lower shoot pruning weights and lower berry weights, while total soluble solids and titratable acidity were not affected. The vine's photosynthetic activity, as well as the soil water content, were partly affected by treatments dependent on the precipitation ahead of the measurement. In parallel, the soil microbial activity was significantly enhanced by a permanent vegetation cover below the vines as compared to herbicide application, a trend which increased with the years of the project. In conclusion, permanent under-vine vegetation strongly promoted soil microbial activity without strong effects on shoot pruning weight, grape yield and quality. In the next step, a functional proof is necessary to characterise the interaction between soil microbial activity, soil water balance and vine nutrition and water status by using sensors for continuous measurements.

Hydrological modeling for landscape and catchment scale applications requires upscaling of soil hydraulic parameters which are generally only available at point scale. We present a case study where hourly root zone soil water content and drainage observations from nine flat, pastoral sites (Waikato and Canterbury regions in New Zealand) were used to develop an upscaling approach to parameterize the soil water balance module of the TopNet catchment model, based on scaling multi-layer soil profile information from the national soil data base, S-map, to the single-layer soil profile used in TopNet. Using a Bayesian calibration approach, the hydraulic behavioral parameters of TopNet's soil water balance module were identified. Of the eleven calibration parameters considered three were found to be insensitive to data (stress point, unsaturated hydraulic conductivity and infiltration rate); three were correlated and could be determined from specific soil water content observations (wilting point, field capacity and drainable water); and five were correlated and could be determined from combined specific soil water content and drainage observations (drainage rate, saturated hydraulic conductivity profile, effective soil depth, soil water holding capacity and wetting front suction). Based on the eight correlated parameters, upscaling functions were then developed to derive suitable model parameters from S-map-hydro for each site. The validity of the upscaling functions was verified at each site. The approach used in this research can be used to parameterize the TopNet model at other similar locations, and also provides a transferable framework to parameterize other catchment-scale hydrology models where point-scale soil hydraulic data available.

The need for improved crop water use efficiency calls for flexible modeling platforms to implement new ideas in plant root uptake and its regulation mechanisms. This paper documents the details of modifying a soil infiltration and redistribution model to include (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) the effect of water stress on plant water uptake, and (d) soil evaporation. The paper also demonstrates strategies of using the modified model to simulate soil water dynamics and plant transpiration considering different sensitivity of plants to soil dryness and different mechanisms of root water uptake. In particular, the flexibility of simulating various degrees of compensated uptake (whereby plants tend to maintain potential transpiration under mild water stress) is emphasized. The paper also describes how to estimate unknown root distribution and rooting depth parameters by the use of a simulation-based searching method. The full documentation of the computer code will allow further applications and new development.

The purpose of this study was to evaluate alternative management practices such as in-field rainwater harvesting (IRWH) and intercropping techniques through conducting on-farm demonstrations. Seven homestead gardens in Thaba Nchu rural communities in the central part of South Africa were selected as demonstration trials. Two tillage systems, conventional (CON) and IRWH, as the main plot, and three cropping systems as sub-plot (sole maize and beans and intercropping) were used to measure water use and radiation use parameters. The water productivity (WP) of various treatments was positively related to the radiation use efficiency (RUE), and the degree of associations varied for different tillage systems. The water use in IRWH was higher by 15.1%, 8.3%, and 10.1% over the CON for sole maize and beans and intercropping, respectively. Similarly, the intercropping system showed water use advantages over the solely growing crops by 5% and 8% for maize and by 16% and 12% for beans under IRWH and CON tillage, respectively. Maximum RUE was found for sole maize and beans under IRWH, higher by 13% and 55% compared to the CON tillage, respectively. The RUE under IRWH tillage was estimated to be 0.65 and 0.39 g DM MJ−1 in sole maize and intercropping, respectively. However, in sole and intercropped beans, the RUE showed higher values of 1.02 g DM MJ−1 and 0.73 g DM MJ−1, respectively. WP and RUE were associated with water deficits and proportional to lower radiation use. This relationship indicates that the intercepted radiation by plants for photosynthesis is directly related to the transpiration rate until radiation saturation occurs. Therefore, the higher water deficit and lesser efficiency in using the radiation available during the season can be improved by practicing IRWH techniques. Furthermore, in semi-arid areas, to enhance the efficiency of water and radiation usage in intercropping management, it is crucial to adjust plant population and sowing dates based on water availability and the onset of rainfall.

Nowadays, changes in precipitation patterns together with the increasing water demand impose a sustainable management where the budget between water availability and demand is positively closed. A parsimonious hydrogeological modelling approach coupled with a soil water balance is developed and applied in order to quantify the hydrological and hydrogeological dynamics in a semi-arid region of the Mediterranean basin. In particular, the present work focuses on the hydrogeological dynamics of the catchment areas of Siedi, Foggia di Rau, Pigonati, and the Palmarini channels located in the Brindisi Plain, Southern Italy. In the last decades, in the Brindisi Plain the anthropization processes as well as the industrial and agricultural development have generated an intensive exploitation of both shallow and deep groundwater resources as well as their qualitative deterioration. A dry hydrologic year (2019–2020) caused a recharge deficit, resulting in a lowering of the groundwater level of the shallow aquifer compared to the expected seasonal value. The results evidence a sensitive natural system, where the variability of the rainfall regime combined with water withdrawal leads to a system that is very vulnerable to climate change impacts, such as the presence of erratic rainfall patterns affecting aquifer recharge. This study represents the first approach to couple a soil moisture balance model and groundwater flow model to assess the impact of changes in rainfall patterns on groundwater recharge for the Brindisi Plain aquifer. The developed integrated hydrogeological model can be applied to other sites with similar hydrogeological features and represents an important tool in order to evaluate the effectiveness of cost-effective sustainable actions for the management of the groundwater resources with respect to land-use practices and socio-economic aspects.

Annual vegetation aboveground net primary productivity (ANPP) exhibits a non‐linear dependence on annual precipitation. A common pattern of non‐linearity, called asymmetry, arises when productivity responses in wet years are larger than declines in dry years. To date, ANPP asymmetry has been attributed primarily to vegetation water stress, an internal ecosystem response to precipitation and soil water availability. However, when quantified via the asymmetry index (AI) estimated from productivity measurements, the asymmetry can be a sampling artefact that arises from a positively skewed annual precipitation distribution. In this paper, we aimed to separate the sampling effect (from external precipitation variability) from the non‐linear response of the system (the internal ecosystem dynamics). We constructed a probabilistic model that integrates the precipitation distribution with the precipitation‐productivity response curve (PPT‐ANPP curve), derived using empirical formulae and a process‐based soil water balance model. The model was used to derive the probability density function of AI and to attribute its shape to the PPT distribution and the PPT‐ANPP response curve. The models were compared to data from 47 grasslands. Results demonstrated that positively skewed precipitation produces a positive AI as a statistical artefact. The non‐linear ecosystem PPT‐ANPP dependence can further enhance or dampen this statistical artefact. In all sites, the precipitation skew highly affected the probability of correctly identifying asymmetry using AI. Observed negative asymmetry arises from a larger soil water holding capacity and positive asymmetry from plant water stress. More robust statistical indicators of non‐linear ecological responses to climate variability are needed to improve ecosystem forecasts. [ABSTRACT FROM AUTHOR]

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A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.

Study region: West Africa, with a focus between 5°W and 5°E. Study focus: The effects of changing climate and CO2 concentration (RCP8.5 between 2000 and 2100) on the West African monsoon are examined using the UPSCALE high-resolution (25 km) global climate model ensembles for present and future climate, combined with the JULES land-surface model. New hydrological insights: Future climate is predicted to have an enhanced summertime Saharan heat low, changing large-scale circulation, causing monsoon rainfall generally to increase. The monsoon progresses further inland and occurs later in the year. UPSCALE rainfall projections indicate that the eastern Sahel becomes wetter (+ 12.2%) but the western Sahel drier (− 13.5%). Future evapotranspiration is reduced across most of West Africa due to the CO2 fertilisation effect causing lower transpiration. Potential groundwater recharge (soil drainage at the bottom of a 3 m deep soil column), is predicted to increase from 0% to 16% of rainfall under present climate, to 1–20% in the future, doubling from ~ 5% to ~ 10% in northern Ghana and the eastern Sahel. Potential recharge increases largely due to increased soil hydraulic conductivity, caused by higher soil moisture resulting from increased rainfall and reduced transpiration. Other factors have only a minor influence on the water balance and potential recharge, including rainfall intensity and land use type. A predicted increase in future potential groundwater recharge is significant as development of groundwater resources is seen as a key means to meet growing water demand in West Africa.

[Display omitted] • Biocrusts increase water evaporation rate up to 33% in laboratory. • Biocrusts raise vapor diffusion rate by 28% and vapor diffusivity by 34%. • Heavy water isotopes are more enriched in moss biocrusts than bare soil. • Modified soil properties of biocrusts are key factors influencing water evaporation. • Increased evaporation rate and vapor diffusivity control water isotopic composition. Evaporation, one of the main components of the water and energy balance between soil and atmosphere, plays a key role in hydrological processes particularly in semi-arid and arid climate regions. As critical living organism communities inhabiting the soil-atmosphere boundary, biocrusts are capable of modifying near-surface soil properties and structure in drylands. However, the roles of biocrusts in mediating soil evaporation still remain greatly controversial, and the literature yet lacks in a systematic assessment. In this study, evaporation experiments were conducted under simulated isothermal and non-isothermal conditions for bare soil and three types of biocrusts (cyanobacterial, moss, and their mixture) sampled from a semi-arid climate region of the Chinese Loess Plateau. During the evaporation, soil temperature and moisture were measured at depths 2, 5, 10, and 15 cm for those biocrusts and bare soil. Their water vapor diffusion process and stable isotopic composition were also analyzed in the laboratory. We found that the measured evaporation yielded 4.9%, 17.5%, and 31.6% higher average evaporation rate for cyanobacterial, cyano-moss, and moss crusts, respectively, when compared to the bare soil. In comparison to bare soil, all types of biocrusts markedly reduced the rate of temperature rise, prolonged the duration of wetting time, and delayed the formation of dry surface layer. The largest regulating effects on soil temperature and moisture were found in the moss crusts instead of cyanobacterial or cyano-moss crusts. The increasing evaporation in biocrusts was attributed to their higher fine particle content, lower bulk density, and greater water holding capacity. Moreover, the water vapor diffusion rate and diffusivity of biocrusts were 18.2% and 16.4% higher than those of bare soil, respectively, which is attributable to the increased total porosity and better soil structure. Additionally, the isotopic composition of soil water (0–50 cm) in bare soil and moss crusts was distributed below the local meteoric water line. The mean δ18O and δ2H in soil water gradually decreased with increasing soil depth, and the moss crusts were more isotopically enriched than bare soil. Based on the enhanced soil evaporation rate, improved vapor diffusivity, and enriched isotopic composition of biocrusts in contrast to bare soil, we conclude that biocrusts exacerbate vapor transport and evaporative loss, and consequently they are crucial surface cover in rebalancing surface ecohydrological and biochemical processes in global drylands. These findings improve our understanding of the complexity of dryland hydrology, and a full consideration should be given in future biocrust studies. [ABSTRACT FROM AUTHOR]