Search

The hydrothermal regime of soils, which are formed on the same type of parent rock under different plant communities in ecosystems of large lysimeters at the Soil Experimental Station of Moscow State University, is characterized. The inter- and intra-annual influence of the vegetation cover on the dynamics of temperature and moisture content in soil horizons is evaluated. It is shown that over a 60-year period after the start of the experiment, the studied soils significantly differ in moisture and temperature conditions. The greatest impact is exerted by the tree layer, due to the precipitation redistribution and the transpiration effect, which significantly decrease soil moisture and lysimetric runoff. There is a 2–3-time difference in the moistening of the upper 20-cm layer and more than 10-time difference in the runoff volume between the driest ecosystem (spruce forest) and the most humid one (fallow). The specific effect of the forest type on the temperature regime of soils is revealed. The temperature is minimal under coniferous ecosystem and is maximal under broad-leaved ecosystem (the difference in the mean annual temperature in the 10-cm soil layer is more than 1.6°С). The role of the grass cover, which reduces temperature extremes and evaporation from the soil surface, is shown. Seasonal features of the effect of the plant cover on the hydrothermal soil regime are assessed.

Crop coefficient (Kc) represents the actual crop growth of the crop. It plays an important role in estimating water requirements at the different growth stages of the crop. However, FAO 56 Penman–Monteith Kc method does not account for spatial heterogeneity and uncertainty for regional climatic conditions significantly. Therefore, this study aims to develop the relation between Kc and normalized difference vegetation index (NDVI) using a linear regression and back calculations. These relationships were adjusted to local conditions using information from survey data obtained during Rabi season (2014–2015). The NDVI–Kc model (r2 = 0.86) has developed using NDVI–Kc from a fine resolution Landsat 8 remote sensing data. NDVI–Kc regression equation was utilized for generating crop coefficient for different month of season. The Vegetation Index-based AET estimated was evaluated with lysimeter data for different crop growth stage across the season. The results have shown that NDVI–Kc estimated AET has been better correlated with NDVI–Kc remote sensing model. Thus, the output of this research can help to calculate actual water demand in a command area and be helpful in allocating water from less demand area toward more demand area.

COEFICIENTE DE CULTIVO PARA CENOURA SOB A PERSPECTIVA DE DIFERENTES MODELOS MATEMÁTICOS DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA MÁRCIO AURÉLIO LINS DOS SANTOS1; THAYSE VALÉRIA E SILVA2; JULIANNA CATONIO DA SILVA3; DANIELLA PEREIRA DOS SANTOS4; CÉLIA SILVA DOS SANTOS5 1Professor do Curso Bacharelado em Agronomia, Universidade Federal de Alagoas - Campus de Arapiraca, Avenida Manoel Severino Barbosa, s/n, Bom Sucesso, 57309-005, Arapiraca, Alagoas, Brasil. E-mail: mal.santo@arapiraca.ufal.br 2Administradora Técnica de Vendas, Iharabras, Avenida Liberdade, 1701, 18087-170, Sorocaba, São Paulo, Brasil. E-mail: thaysevaleria15@gmail.com 3 Doutoranda em Agronomia (Produção Vegetal), Laboratório de Irrigação e Agrometeorologia,, Universidade Federal de Alagoas - Centro de Ciências Agrárias, BR-104, 57100-000, Rio Largo, Alagoas, Brasil. E-mail: julianna_cds@hotmail.com 4Doutora em Engenharia Agrícola pela Universidade Federal Rural de Pernambuco - Campus Dois Irmãos, 52171-900, Recife, Pernambuco, Brasil. E-mail: daniellapsantos@hotmail.com 5Doutora em Engenharia Agrícola pela Universidade Federal Rural de Pernambuco - Campus Dois Irmãos, 52171-900, Recife, Pernambuco, Brasil. E-mail: celia_agron@hotmail.com 1 RESUMO O coeficiente de cultivo (Kc) é um parâmetro essencial para o dimensionamento e manejo dos sistemas de irrigação e uso racional da água. Dessa forma, o objetivo neste trabalho foi determinar o coeficiente de cultivo da cenoura (Daucus carota L.) por meio de diferentes modelos matemáticos da evapotranspiração de referência no Agreste alagoano. O experimento foi realizado na área experimental do Campus da Universidade Federal de Alagoas (UFAL), Arapiraca-AL. Foram utilizados três lisímetros de drenagem, instalados em canteiro com dimensões de 3,5 x 1,0 m de comprimento e largura respectivamente com área total de 3,5 m2. O Kc foi obtido pela relação entre a evapotranspiração da cultura (ETc) e a evapotranspiração de referência (ETo) estimada pelos métodos de Penman-Monteith, padrão-FAO (PM), Hargreaves-Samani (HS), Radiação Solar (RS), Blaney-Criddle (BC) e de Priestley-Taylor (PT). Os valores de Kc obtidos foram: KcPM (0,61; 1,00; 1,26 e 0,99), KcHS (0,63; 1,09; 1,27 e 0,94), KcRS (0,65; 1,03; 1,36 e 1,06), KcBC (0,69; 1,11; 1,52 e 118) e KcPT (0,67; 1,08; 1,25 e 0,99) para as fases inicial, crescimento, intermediária e final, respectivamente. Na ausência de informações agrometeorológicas para se estimar a ETo pelo método padrão, recomendam-se utilizar os valores de obtidos pelo método de Blaney-Criddle. Keywords: Daucus carota, lisimetria, dados climáticos, manejo da irrigação. SANTOS, M. A. L.; SILVA, T. V.; SILVA, J. C.; SANTOS, D. P.; SANTOS, C. S. CARROT CROP COEFFICIENT FROM THE PERSPECTIVE OF DIFFERENT MATHEMATICAL MODELS OF REFERENCE EVAPOTRANSPIRATION 2 ABSTRACT The crop coefficient (Kc) is an essential parameter for the design and management of irrigation systems and rational reasonable water. Thus, the aim of the present work was to determine the crop coefficient of the carrot (Daucus carota L.) through different mathematical models of the reference evapotranspiration in the Agreste alagoano. The experiment was performed in the experimental area of the Campus of the Federal University of Alagoas (UFAL), Arapiraca-AL, Brazil. Three lysimeters of drainage were used, installed on a bed with dimensions of 3.5 x 1.0 m in length and width, respectively, with a total area of 3.5 m2. The Kc was obtained from the relationship between crop evapotranspiration (ETc) and reference evapotranspiration (ETo) estimated using the methods of Penman-Monteith-FAO (PM), Hargreaves-Samani (HS), Solar Radiation (SR), Blaney-Criddle (BC) and Priestley-Taylor (PT). The values of Kc obtained were KcPM (0.61; 1.00; 1.26 and 0.99), KcHS (0.63; 1.09; 1.27 and 0.94), KcSR (0.65; 1.03; 1.36 and 1.06), KcBC (0.69; 1.11; 1.52 and 118) and KcPT (0.67; 1.08; 1.25 and 0.99) for the initial, growth, intermediate and final phases, respectively. In the absence of agrometeorological information to estimate ETo by Penman-Monteith-FAO method, it is recommended to use the values obtained by Blaney-Criddle ETo method. Keywords: Daucus carota, lysimetry, climate data, irrigation management.

Desertification in semi-arid regions is currently a global environmental and societal problem. This research attempts to understand whether a 40-year-old rain-fed Artemisia sphaerocephala Krasch sand-fixing land as part of the Three North Shelterbelt Program (3NSP) of China can be developed sustainably or not using a newly designed lysimeter to monitor the precipitation-induced deep soil recharge (DSR) at 220 cm of depth. Evapotranspiration is calculated through a water balance equation when precipitation and soil moisture data are collected. A comparison of soil particle sizes and soil moisture distributions in artificial sand-fixing land and neighboring bare land is made to assess the impact of sand-fixing reforestation. Results show that such a sand-fixing reforestation results in a root system being mainly developed in the horizontal direction and a changed soil particle distribution. Specifically, the sandy soil with 50.53 % medium sand has been transformed into a sandy soil with 68.53 % fine sand. Within the Artemisia sphaerocephala Krasch sand-fixing experimental area, the DSR values in the bare sand plot and Artemisia sphaerocephala Krasch plot are respectively 283.6 and 90.6 mm in wet years, reflecting a difference of more than 3 times. The deep soil layer moisture in semi-arid sandy land is largely replenished by precipitation-induced infiltration. The DSR values of the bare sandy land plot and Artemisia sphaerocephala Krasch plot are respectively 51.6 and 2 mm in dry years, a difference of more than 25 times. The proportions of DSR reduced by Artemisia sphaerocephala Krasch are 68.06 % and 96.12 % in wet and dry years, respectively. This research shows that Artemisia sphaerocephala Krasch in semi-arid regions can continue to grow and has the capacity to fix sand. It consumes a large amount of precipitated water and reduces the amount of DSR considerably.

The tropical arboreal species Brazilian mahogany (Swietenia macrophylla) is very important economically and ecologically, for which understanding ecophysiological variables such as sap flow will improve understanding of the species and its cultivation. This paper aims to measure uncertainties (U) involved in the application of the heat ratio method for determining sap flow in Brazilian mahogany using sets of heating probes and thermometers installed on plants of 18 months of age, cultivated in Yellow Latosol, under a weighing lysimeter and located in a protected environment. The uncertainty in sap flow was calculated as the combination of uncertainty in the thermal diffusivity (Uk), conductive section (USc) and corrected sap velocity (UVc). Uk had greater weight in determining the flow of sap in Brazilian mahogany, when compared to USc and UVc. The thermal diffusivity during the cycle, or period evaluated, must be adjusted to improve the accuracy of the heat ratio method because the sap flow overestimated transpiration by 15.0%. When soil water was optimal In addition, the vapor pressure deficit linearly and indirectly influenced the SF with a difference of 14.6%.

Groundwater recharge is critical to water circulation in arid and semi-arid regions. The accurate determination of groundwater recharge is required for assessing water resources and effectively managing groundwater, especially in water-limited areas. Based on field experiments and numerical models in a semi-arid region, this study assessed the effect of non-isothermal flow on groundwater recharge. A lysimeter was used in the Mu Us Desert, northwestern China, to monitor groundwater recharge from 1 June to 30 September 2018. The numerical models (isothermal and non-isothermal models) were calibrated with the measured soil moisture and soil temperature. Groundwater recharge was found to take up nearly 29% of rainfall. The non-isothermal model was capable of accurately assessing groundwater recharge based on the accurate calculation of evaporation. The isothermal model, however, underestimated the groundwater recharge by 13.2% and overestimated the evaporation by 16.2%. The isothermal model overestimated evaporation during the drying process. In contrast, cumulative net recharge was underestimated after heavy rainfall events. It was therefore suggested that the non-isothermal flux should be considered in semi-arid regions, especially when assessing groundwater recharge.

Accurate estimation of evapotranspiration (ET) is an important factor in water management, especially in irrigated agriculture. Accurate irrigation scheduling requires accurate estimation of ET. The objective of this study was to estimate the actual evapotranspiration (ETa) by the pySEBAL model and to compare it with the actual evapotranspiration measured by the lysimeter method of soybean crop in Adana, Turkey. Five Landsat 5 Thematic Mapper (TM) images and weather data were used for this study to estimate actual evapotranspiration by the pySEBAL model. The results showed a good relationship between ETa estimated by the pySEBAL model and ETa measured by the lysimeter method, with an R2 of 0.73, an RMSE of 0.51 mm.day−1, an MBE of 0.04 mm.day−1 and a Willmott’s index of agreement (d) of 0.90. Based on this study, there is a good relationship between the actual evapotranspiration estimated by the pySEBAL model and the actual evapotranspiration measured by the lysimeter method. Consequently, ETa of soybean crop can be estimated with high accuracy by the pySEBAL model in Adana, Turkey.

Accurate estimation of reference evapotranspiration (ETo) is profoundly crucial in crop modeling, sustainable management, hydrological water simulation, and irrigation scheduling, since it accounts for more than two-thirds of global precipitation losses. Therefore, ETo-based estimation is a major concern in the hydrological cycle. The estimation of ETo can be determined using various methods, including field measurement (the scale of the lysimeter), experimental methods, and mathematical equations. The Food and Agriculture Organization recommended the Penman-Monteith (FAO-56 PM) method which was identified as the standard method of ETo estimation. However, this equation requires a large number of measured climatic data (maximum and minimum air temperature, relative humidity, solar radiation, and wind speed) that are not always available on meteorological stations. Over the decade, the artificial intelligence (AI) models have received more attention for estimating ETo on multi-time scales. This research explores the potential of new hybrid AI model, i.e., support vector regression (SVR) integrated with grey wolf optimizer (SVR-GWO) for estimating monthly ETo at Algiers, Tlemcen, and Annaba stations located in the north of Algeria. Five climatic variables namely relative humidity (RH), maximum and minimum air temperatures (Tmax and Tmin), solar radiation (Rs), and wind speed (Us) were used for model construction and evaluation. The proposed hybrid SVR-GWO model was compared against hybrid SVR-genetic algorithm (SVR-GA), SVR-particle swarm optimizer (SVR-PSO), conventional artificial neural network (ANN), and empirical (Turc, Ritchie, Thornthwaite, and three versions of Valiantzas methods) models by using root mean squared error (RMSE), Nash-Sutcliffe efficiency (NSE), Pearson correlation coefficient (PCC), and Willmott index (WI), and through graphical interpretation. Through the results obtained, the performance of the SVR-GWO provides very promising and occasionally competitive results compared to other data-driven and empirical methods at study stations. Thus, the proposed SVR-GWO model with five climatic input variables outperformed the other models (RMSE = 0.0776/0.0613/0.0374 mm, NSE = 0.9953/ 0.9990/0.9995, PCC = 0.9978/0.9995/0.9998 and WI = 0.9988/0.9997/0.9999) for estimating ETo at Algiers, Tlemcen, and Annaba stations, respectively. In conclusion, the results of this research indicate the suitability of the proposed hybrid artificial intelligence model (SVR-GWO) at the study stations. Besides, promising results encourage researchers to transfer and test these models in other locations in the world in future works.

Research into the unsaturated zone and groundwater recharge can greatly improve understanding of hydrological processes and assist in sustainable groundwater management. Groundwater recharge of the Ljubljana Field aquifer, a coarse-gravel porous aquifer in Slovenia, was estimated with reference to soil characteristics, outflow data from a weighing lysimeter, and water-table fluctuation. The specific yield of the upper unsaturated zone determined from soil characteristics was 0.141 for the top soil layer (0–0.35 m), between 0.042 and 0.066 for the layer below the top soil (0.35–1.3 m), and between 0.239 and 0.219 for the underlying upper coarse layer. During long dry periods, especially in combination with times of high plant-water requirements, only substantial precipitation events directly contribute to considerable groundwater recharge, as ‘substantial precipitation’ is defined as those rainfall events that fill storage and exceed retention capacity of the upper soil layer. Lysimeter measurements show that 50% of the precipitation is lost by evapotranspiration and the other 50% contributes to groundwater recharge. Most infiltrated water was stored for a short time in the unsaturated zone and did not result in a significant discharge from the lysimeter. Average specific yield, calculated using the water-table fluctuation method, was 0.144. The nature of the gravely unsaturated zone is that once the retention buffer of the soil is exceeded, the water front travels through relatively quickly, which can be seen as an advantage for recharge or a disadvantage for prevention of groundwater pollution.

Evapotranspiration (ET) from riparian vegetation can be difficult to estimate due to relatively abundant water supply, spatial vegetation heterogeneity, and interactions with anthropogenic influences such as shallower groundwater tables, increased salinity, and nonpoint source pollution induced by irrigation. In semiarid south‐eastern Colorado, reliable ET estimates are scarce for the riparian corridor that borders the Arkansas River. This work investigates relationships between the riparian ecosystem along the Arkansas River and an underlying alluvial aquifer using ET estimates from remotely sensed data and modelled water table depths. Results from a calibrated, finite‐difference groundwater model are used to estimate weekly water table fluctuations in the riparian ecosystem from 1999 to 2009, and estimates of ET are calculated using the Operational Simplified Surface Energy Balance (SSEBop) model with over 200 Landsat scenes covering over 30 km² of riparian ecosystem along a 70‐km stretch of the river. Comparison of calculated monthly SSEBop ET to estimated alfalfa reference ET from local micrometeorological station data indicated statistically significant high linear correspondence (R² = .87). Daily calculated SSEBop ET showed statistically significant moderate linear correspondence with data from a local weighing lysimeter (R² = .59). Simulated monthly SSEBop ET values were larger in drier years compared with wetter years, and ET variability was also larger in drier years. Peak ET most commonly occurred during the month of June for all 11 years of analysis. Relationships between ET and water table depth showed that peak monthly ET was highest when groundwater depths were less than about 3 m, and ET values were significantly lower for groundwater depths greater than 3 m. Negative sample Spearman correlation highlighted riparian corridor locations where ET increased as a result of decreased groundwater depths across years with different hydroclimatic conditions. This study shows how a combination of remotely sensed riparian ET estimates and a regional groundwater model can improve our understanding of linkages between riparian consumptive use and near‐river groundwater conditions influenced by irrigation return flow and different climatic drivers.

HighlightsSWAT soil water assessment was performed using soil water measurements.Dryland SWAT model soil water content was greater than the irrigated SWAT model.Using SWAT soil water estimates for real-time (daily) irrigation management purposes with the existing SWAT soil water subroutines and available soils data is considered risky.The surface layer showed the greatest soil water variability compared to deeper layers.Abstract. Soil water content (SWC) is a challenging measurement at the field, watershed, and regional scales. Soil and Water Assessment Tool (SWAT) soil water estimates were evaluated at three locations: the St. Joseph River watershed (SJRW) in northeast Indiana, the USDA-ARS Conservation and Production Research Laboratory (CPRL) at Bushland, Texas, and the USDA-ARS Limited Irrigation Research Farm (LIFR) at Greeley, Colorado. The soil water estimates were evaluated under two scenarios: (1) for the defined soil profile, and (2) by individual layer. Each site’s soil water assessment was performed based on the existing management conditions during each experiment, whether dryland or irrigated, and for various periods depending on SWC measurement availability at each site. The SWAT soil water was evaluated as follows: the Indiana site was evaluated under dryland conditions using daily soil water observations for one year; the Texas site was evaluated for a ten-year period under irrigated and dryland conditions using weekly soil water observations from four lysimeters; and the Colorado site was evaluated under irrigated conditions for a four-year period. The simulated soil water was evaluated by comparing the model simulations with observed daily and weekly soil water measurements at the three sites. Based on the results, even though all the SWAT models were considered to perform as good models following calibration (streamflow, ET, etc.), the soil water simulations were unacceptable for the defined soil profile and for individual layers at the three sites. Deeper soil layers had observations greater than field capacity values, indicating poor soil parameterization. The dryland model had greater water content than the irrigated model, contradicting the soil water measurements. This greater soil water simulation with the dryland model is a result of SWAT model uncertainties with ET reduction under dryland conditions due to water stress. This study indicated that soil water estimation using the default SWAT soil water equations has many sources of uncertainties. Two apparent sources resulted in the SWAT model’s poor performance: (1) SWAT soil water routines that do not fully represent soil water moving between layers to meet plant demand and (2) uncertainty in soil parameterization. Keywords: Hydrologic modeling, Soil moisture, Soil moisture sensor, Soil water, Soil and Water Assessment Tool.

As a result of global climate change, heavy rainfall events and dry periods are increasingly occurring in Germany, with consequences for the water and solute balance of soils to be expected. The effects of climate change on nitrogen and carbon leaching were investigated using 21 non-weighable manually filled lysimeters of the UFZ lysimeter facility Falkenberg, which have been managed since 1991 according to the principles of the best management practices and organic farming. Based on a 29-year dataset (precipitation, evaporation, leachate, nitrate and dissolved organic carbon concentrations), the lysimeter years 1995/96, 2018/19, and 2003/04 were identified as extremely dry years. Under the climatic conditions in northeastern Germany, seepage fluxes were disrupted in these dry years. The reoccurrence of seepage was associated with exceptionally high nitrogen concentrations and leaching losses, which exceeded the current drinking water limits by many times and may result in a significant risk to water quality. In contrast, increased DOC leaching losses occurred primarily as a result of increased seepage fluxes.

The Jinghe River Basin is an important grain-producing area in northwest China; yet, serious soil erosion and water shortage problems have greatly limited the development of agriculture in the region. Evapotranspiration (ET) is a key component of rational water resources planning and water cycle mechanism exploration; yet, studies in this region have mainly focused on rainfall and runoff sand transport, neglecting the role of ET. Therefore, to understand the characteristics of ET in the Jinghe River basin, we estimated the ET during the vegetation growing season (April to October) in 2018 using the surface energy balance system (SEBS) based on remote sensing images and meteorological data, and analyzed the characteristics of its spatio-temporal distribution and its relationship with environmental factors. The results showed that (1) SEBS has good applicability in the study area, with R1 between 0.57 and 0.77, RMSE between 0.98 and 1.15 mm / d, and MRE between 24% and 36% as verified with the lysimeter and ET products; (2) on the basin scale, the average daily ET showed a unimodal distribution with time, with variations ranging from 1.6 to 4.1 mm while spatially it showed that the mountainous forest and river catchment areas were overall higher than the loess plateau and hilly gully areas; (3) on the landscape scale, the vegetation with the highest average daily ET was broad-leaved forest, and the lowest was grassland. The vegetation with the highest ecological water demand was cultivated vegetation, and the lowest was meadow; (4) correlation analysis showed that rainfall, temperature, sunshine hours, and vegetation cover were positively correlated with ET. Among them, rainfall and temperature have the strongest correlation with ET and maybe the main factors affecting ET in the Jinghe River Basin.

Non-rainfall water (NRW), defined here as dew, hoar frost, fog, rime and water vapor adsorption, might be a relevant water source for ecosystems, especially during summer drought periods. These water inputs are often not considered in ecohydrological studies, because water amounts of NRW events are rather small and therefore difficult to measure. Here we present a novel micro-lysimeter (ML) system and its application which allows to quantify very small water inputs from NRW with an unprecedented high accuracy of ±0.25 g, which corresponds to ±0.005 mm water input. This is possible with an improved ML design paired with individual ML calibrations in combination with high-frequency measurements at 3.3 Hz and an efficient low-pass filtering to reduce noise level. With a set of ancillary sensors, the ML system furthermore allows differentiating between different types of NRW inputs: dew, hoar frost, fog, rime and the combinations among these, but also additional events when condensation on leaves is less probable, such as water vapor adsorption events. In addition, our ML system design allows to minimize deviations from natural conditions in terms of canopy and soil temperatures, plant growth and soil moisture. This is found to be a crucial aspect for obtaining realistic NRW measurements in short-statured grasslands. Our ML system has proven to be useful for high-accuracy, long-term measurements of NRW on short-statured vegetation like grasslands. Measurements with the ML system at a field site in Switzerland showed that NRW input occurred frequently with 127 events over 12 months, with a total NRW input of 15.9 mm. High average monthly NRW inputs were measured during summer months, suggesting a high ecohydrological relevance of NRW inputs for temperate grasslands., Hydrology and Earth System Sciences Discussions, ISSN:1812-2116, ISSN:1812-2108

Inappropriate drainage and agricultural development on tropical peatland may lead to an increase in methane (CH4) emission, thus expediting the rate of global warming and climate change. It was hypothesized that water table fluctuation affects CH4 emission in pineapple cultivation on tropical peat soils. The objectives of this study were to: (i) quantify CH4 emission from a tropical peat soil cultivated with pineapple and (ii) determine the effects of water table depth on CH4 emission from a peat soil under simulated water table fluctuation. Soil CH4 emissions from an open field pineapple cultivation system and field lysimeters were determined using the closed chamber method. High-density polyethylene field lysimeters were set up to simulate the natural condition of cultivated drained peat soils under different water table fluctuations. The soil CH4 flux was measured at five time intervals to obtain a 24 h CH4 emission in the dry and wet seasons during low- and high-water tables. Soil CH4 emissions from open field pineapple cultivation were significantly lower compared with field lysimeters under simulated water table fluctuation. Soil CH4 emissions throughout the dry and wet seasons irrespective of water table fluctuation were not affected by soil temperature but emissions were influenced by the balance between methanogenic and methanotrophic microorganisms controlling CH4 production and consumption, CH4 transportation through molecular diffusion via peat pore spaces, and non-microbial CH4 production in peat soils. Findings from the study suggest that water table fluctuation at the soil–water interface relatively controls the soil CH4 emission from lysimeters under simulated low- and high-water table fluctuation. The findings of this study provide an understanding of the effects of water table fluctuation on CH4 emission in a tropical peatland cultivated with pineapple.

To investigate carbon (C) and nitrogen (N) dynamics in seasonally frozen soils under saline and shallow groundwater supply conditions, in-situ lysimeter experiments with different groundwater table depths (WTD = 1.8 and 2.2 m) were conducted in Inner Mongolia, China during the wintertime of 2012–2013. Changes in soil organic C and total N in multiple layers during various periods, as well as their relationships with soil water, salt, and heat dynamics were analyzed. Accumulation of soil organic C and total N during freezing periods was strongly related to water and salt accumulation under temperature and water potential gradients. Water and salt showed direct influences on soil C and N dynamics by transporting them to upper layer and changing soil microbial activity. Salt accumulation in the upper layer during freezing and thawing of soil affected microbial activity by lowering osmotic potential, resulting in lower C/N ratio. Nitrogen in soil tended to be more mobile with water during freezing and thawing than organic C, and the groundwater table also served as a water source for consecutive upward transport of dissolved N and C. The changes in C and N in the upper 10 cm soil layer served as a good sign for identification of water and salt influences on soil microbial activity during freezing/thawing.

Over half of the irrigated land in the US, 11.5 million ha, is irrigated with center pivot and linear move systems. Because of this, minor changes in the operation efficiency of these systems can have large impact on overall water conservation. The objective of this study was to evaluate the water application efficiency (WAE) of low and of mid elevation spray application (LESA and MESA) using catch can test and drainage lysimeters, and develop governing equations based on the weather variables. A three-year (2015–2017) field study was conducted at the Washington State University Research and Extension Center, near Prosser. Catch cans were used to collect the fraction of total irrigation-water applied that reached the ground surface as WAE and drainage lysimeters to measure the overall water loss (OAWL) and wind drift and evaporation losses (WDEL), (WDEL = 100-WAE). Air temperature (Ta), relative humidity (RH), short-wave global irradiance (Rg), wind speed (WS), and calculated vapor pressure deficit (VPD) were used as the input weather variables to mixed modeling technique. Results showed that on average 21% more irrigation-water reached the ground with LESA than with MESA systems. Lysimetric measurements showed on average a 16% efficiency difference between MESA and LESA. The monthly WAE differences between MESA and LESA increased from 12 to 30% during the hot summer months and thereafter decreased, from 30 to 9%. The warmer and drier year of 2015 had the highest annual average values of WDEL of 17% for LESA and 19% for MESA. Results indicated a relatively constant WAE for LESA regardless of weather conditions. Mixed modelling showed that VPD was the only significant predictor (P

Groundwater recharge by precipitation is often assumed by practitioners as well as scientists to be a slow process of filtration through layers of uniform texture analogous to Darcy’s law. In most basins, however, rainwater also finds its way through macropores and preferential pathways to the shallow unconfined aquifers within hours of falling. Recharge phases may extend over several days, increasing groundwater levels, stored volume and hence baseflows into adjoining rivers. In this study, groundwater recharge and storage are computed from baseflow as separated with a nonlinear reservoir algorithm from time series of daily flows at gauging stations in northern Germany. Results are compared to groundwater level fluctuation in the catchments and to daily seepage rates measured in a lysimeter station. Peak times of the fast transfer of rain water through the vadose zone are generally the same. However, while recharge from baseflow ends when baseflow assumes its typical recession, the attenuation of lysimeter seepage may last much longer. The volume of lysimeter seepage is generally higher than the recharge in catchments due not only to different vegetation but also to rim effects impeding direct runoff. Furthermore, the lysimeter walls allow vertical fluxes only. Without further evidence or improved devices, lysimeter seepage should therefore not be indicated as groundwater recharge for the site or catchment. Findings also indicate that the shape of derived recharge unit responses is practically time invariant but with a strong seasonal variation in the recharge-rainfall ratio of precipitation events.

The evapotranspiration process is critical to studies on the water balance and water demand of crops and can be determined by several methods. A widely-used method, despite its high installation costs, is weighing lysimeters, which consists of a box over a balance connected to a load cell that monitors variations in the soil-water-plant-atmosphere system. The aim of this study was to develop and calibrate six weighing lysimeters (with dimensions of 1.5 x 1.5 x 1.2 m each) by high precision load cells, testing their ability to measure water mass changes in field conditions and cultivated with common bean (Phaseolus vulgaris L.), in the city of Tangará da Serra, in the state of Mato Grosso, Brazil. All lysimeters showed coefficients of determination higher than 0.99, as well as Willmott indexes, correlation and high confidence indexes, indicating that the equipment is suitable for measuring mass variations in water balance and evapotranspiration studies, representing the reality which occurred in the field.

Dune belts are crucial for the recharge of coastal aquifers. In spite of their hydrological relevance for the maintenance of precious natural wetland and wildlife environments and a range of other ecosystemservices, only limited knowledge of soil water dynamics in dune belts is currently available. This study presents soilwater balance components measured during one hydrological year using a high precision meteo-lysimeter with lower boundary control installed in a coastal dune belt under a dry subhumid climate in southern Spain close to the Atlantic Ocean. The site is equipped with a cylindrical lysimeter of 1 m2 surface and 1.50 m height (METER Group, Inc. USA) and a weighing resolution of 10 g, 2 SC650 soil moisture sensors (Campbell Scientific, Logan, UT) and 1 automatic meteorological station. The lower boundary condition at the bottom of the lysimeter is controlled at 1.4 m depth by a bidirectional peristaltic pump to maintain field conditions. Results show a recharge rate of 64% of the precipitation measured by the lysimeter. Diurnal oscillations of the measured upper boundary flow during days without rainfall represented vapor adsorption and real evaporation rates ranging between 0.3 and 0.4 mm/day and 0.4 and 0.6 mm/day, respectively throughout the whole year summing up an annual vapor adsorption of 77mm. The measured precipitation of the lysimeter exceeded pluviometer data by 13% as a result of vapor adsorption. The presented results provide a precise balance of soilwater components in a coastal dune belt including the relevant contribution of vapor flow., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departamento de Física Aplicada, Universidad de Córdoba, España, Centro Alameda del Obispo, Investigación y Formación Agraria y Pesquera, España, Instituto Geológico y Minero de España, España

Evapotranspiration (ET) constitutes the largest loss of water from subtropical grassland and wetland ecosystems, yet estimates have high uncertainty at the landscape scale as there is little information on plant water use. A major reason for this is the complexity and expense of field-based ET quantification methods such as agricultural lysimeters and eddy covariance systems. This study developed two different low-cost lysimeters – weighing-type and water level based, to measure ET under controlled conditions for single species as well as mixed grassland and wetland communities. Lysimeters were placed in an open sided shadehouse with a transparent roof to exclude rainfall. ET values were then compared with (i) Actual ET measurements from an eddy covariance tower onsite, (ii) vapor transport-based ET models - FAO Penman-Monteith, Modified Turc and Abtew Simple Radiation models, and (iii) ET data from the Florida Automated Weather Network. Both weighing-type and water level lysimeters showed seasonal patterns and annual magnitudes similar to the other ET methods. Annual ET measurements from weighing lysimeters (881-1278 mm for four plant species, n=5 per species) and water level lysimeters (1085 mm, n = 30) were similar to model estimates (1000-1200mm). Actual ET from eddy covariance was 722 mm for ten months (missing data for February and March), similar to lysimeter measurements for the dominant grass Paspalum notatum (885mm for 10 months). Low-cost lysimeters can easily inform regional ET models/remote sensing data lacking field validation and thus are potentially useful for water resources and ecosystem management in data-poor regions of the world.

The attempt was to design and develop an automatic closed canopy chamber (ACCC) having dimension of 1.2 m×1.2 m× 1.2 m for crop evapotranspiration measurement by using transparent acrylic sheet of 4 mm thickness. Between two small fans a temperature and relative humidity sensor was used to measure vapor density. The intermediate circuit was developed for making automation system in ACCC. The arduino based coding was developed as per desired logic operation. The top lead of chamber was automatically closed for 2 minutes when inside and outside temperature and relative humidity of ambient air were similar. During measurement mode of ACCC, the two fans were started automatically. After measurement mode, fans were automatically stopped and top lead was opened. The ACCC was calibrated by evaporating mass of water from water filled tray which was placed inside the automatic closed canopy chamber. The validation of the developed ACCC were made using micro-lysimeters (MLS) having size of 0.2 m × 0.2 m × 0.2 m by growing shallow rooted crop like fenugreek. The depth of irrigation was computed based on soil moisture content before irrigation and field capacity. The field testing of ACCC was made by placing chamber in plots of fenugreek crop. The irrigation was applied by drip irrigation as per crop water consumption. The sensor sensed and recorded the instantaneous temperature and relative humidity at 1 second interval for 24 hours. Two sample t-tests were done to compare the data pair of crop evapotranspiration obtained by the MLS inside the ACCC with that of outside the ACCC to ascertain whether there is any effect of the change in micro-climate for a short period of 2 minute on the crop growth physiological processes. Also, the data pair of crop evapotranspiration measured by the MLs, ACCC using the sensor data of temperature-relative humidity were compared and statistically analyzed through t-test. Similarly, the data pair of ETC measured by the FWB (Field Water Balance Method) and ACCC using the sensor data of temperature-relative humidity were also compared and statistically analyzed through t-test. The calibration factor of the ACCC was found as 1.666. The results revealed that there was no significant difference in the crop evapotranspiration measured by the MLs inside and outside ACCC. Also in case of validation and field testing of ACCC, there were no significant difference between the ETC measured by the ACCC, MLs and FWB at 95 percent confidence level. This implies that there are no effects of the change in micro-climate for a short period of 2 minutes in the chamber, on the plant physiological processes. The ETc rate of fenugreek increases as sun rises and reaches the peak after one to two hour from mid-day and then continuously decreases with time. During validation and field testing of ACCC, the fenugreek crop coefficients varied from 0.72 to 1.04 and 0.69 to 1.02 respectively. The developed ACCC is portable as well as more comfortable and cost effective compared to the lysimeter for the measurement of the actual crop evapotranspiration and the crop coefficient.

The use of biochar has increased worldwide in the last years due to its good results for several soil quality indicators. However, restoration potential depends on the type and amount of biochar for each specific soil and land use. In order to investigate this restoration potential differential, we conducted an experiment where we amended two contrasting degraded soils with the same biochar. We installed a controlled and fully randomized percolation lysimeter experiment (3 replicates) with 15 lysimeters on a moderately steep slope angle, monitored for one year. Two types of soil were collected, a low organic matter, hydrophilic vineyard soil and a high organic matter, hydrophobic forest soil. Biochar was applied at 4% for both soils, and an additional treatment at 2% for the forest soil only. Selected soil quality indicators are: soil organic matter, medium weight diameter, aggregate stability, bulk density, pH, electric conductivity, potassium (K), phosphorus (P), soil water repellency, biomass quality. The present study comprises four data collections in different seasons along the year, enabling to compare the development of the biochar effects on different types of soil and its short- and medium-term behaviour.

Lime tree growing area is increasing in Mediterranean temperate regions. In these areas, climate change scenario is expected to raise air temperature and water shortages. Such scenario requires new approaches to implement a precision irrigation in agriculture. In order to use water more efficiently, it becomes necessary to accurately determining the crop water needs, which are estimated by crop evapotranspiration computations (ETc). In this study the ETc of young lime trees grown under Mediterranean conditions were determined using the soil water balance method. For this purpose, two-year old lime trees (Citrus latifolia Tan., cv. Bearss) grafted on C. macrophylla rootstock were cultivated in pot-lysimeters, equipped with capacitance and granular matric sensors for real-time monitoring of the soil water status. Irrigation, drainage, and pot weight were also monitored continuously. All measurements were integrated into a telemetry platform. Agro-meteorological variables, plant water status (stem (Ψstem) and leaf (Ψleaf) water potentials), and leaf gas exchange parameters (stomatal conductance (gs) and net photosynthesis (Pn)) were measured. Along the experiment, an automated irrigation protocol based on volumetric soil water content (θv) threshold values were programmed, guaranteeing an adequate lime tree water status. Irrigation dose was calculated based on a feed-back strategy maintaining θv within 30% management allowed depletion.During the experimental period, the lime trees were well irrigated as revealed midday Ψstem values that were maintained above -0.8 MPa. Also, the mean seasonal values of ≈ 7 µmol m−2 s−1 and 80 mmol m−2 s−1, for Pn and gs, respectively, indicated optimal gas exchange values. The computed water balance parameters yielded values for the crop evapotranspiration from 0.25to 2.56 mm day-1, in winter and summer months, respectively, with maximum values in July when evaporative demand conditions were the highest. This soil water balance was daily validated by the pot weight balance through the year.In conclusion, the automated irrigation of young potted lime trees, using soil water content as a control system variable, has ensured an adequate lime tree water status. A simple, robust weighing/drainage lysimeter, with real-time monitoring of the soil water balance parameters, has been proved practical and economical tool for crop evapotranspiration measurements.Acknowledgments: This work was funded by Spanish Agencia Estatal de Investigación (PID2019-106226RB-C2-1/AEI/10.13039/501100011033) and Fundación Séneca, Región de Murcia (19903/GERM/15) projects.

Sustainable Drainage Systems (SuDS) are a widely adopted approach for managing excess urban runoff by intercepting, retaining and attenuating the flow of water through the built environment, playing a key role in reducing urban flood risk. Vegetated bioretention cells (‘rain gardens’) are one of the most simple, practical and commonly implemented SuDS options and can be easily retrofitted into urban spaces to deal with surface water from paved areas. Although current UK and international guidance provides design guidance for SuDS, no quantitative indications on their hydrological performance are currently available. This study aims to provide evidence to assess the effectiveness of such systems to support optimal implementation of vegetated bioretention cells for stormwater management. Four purpose built, large-scale lysimeter experiments (2.0 m x 2.0 m, each divided into two isolated 1.0 m x 2.0 m cell pairs) were designed to provide long-term monitoring data of key hydrological variables and demonstrate the capacity and effectiveness of monitored bioretention systems. The lysimeters were filled with an engineered soil profile consisting of a surface SuDS substrate (700 mm depth) to sustain vegetation growth and store/attenuate flows, and drainage layers (300 mm depth) consisting of a fine gravel transition layer to prevent the movement of fine sediments and a course gravel base layer to allow free drainage into gauged outflow units. Each of the lysimeter cells feature a dense sensor network, allowing spatiotemporal soil-atmosphere interactions to be observed and changes in relation to rainfall events to be quantified. Tipping bucket rain gauges situated on each of the lysimeters allow the quantification of local precipitation inflows, which are also analysed in the context of site-wide weather monitoring stations to calculate Penman-Monteith reference evapotranspiration. Outflow from the drainage layer of each lysimeter cell is measured using an outflow gauge. Additionally, a network of in-situ soil sensors were deployed throughout the substrate profile at various depths to quantify soil water movement and changes in volumetric water content, soil temperature, electrical conductivity, soil-water potential and hydrostatic water level in accordance with localised weather conditions. Quantifying inflows, storages and losses allows an understanding of the lysimeter mass balance. Further, each of the lysimeter cell pairs were planted with different planting styles (unvegetated control, reference short grass and two uniform mono-cropped shrub species) to provide differing reference evapotranspiration scenarios and to understand the influence of vegetation on bioretention cell performance. This paper outlines the commissioning of a large-scale lysimeter study at the National Green Infrastructure Facility and presents results from mid-2020 onwards, highlighting the hydrological performance of the bioretention cells under a range of natural storm events and climatic conditions. Lysimeter mass balance and retention efficiencies are presented for each of the vegetation scenarios. Further, differences in soil-water retention ability between the lysimeters are examined in relation to the efficiency of various planting styles and their comparative evapotranspirative behaviour. Working together with a range of stakeholders involved in UK SuDS schemes, this work is helping to inform design criteria and anticipated bioretention cell performance using a quantified evidence base.

A diverse size- and matter spectrum of inorganic, organo-mineral and organic substances, and dissolved, colloidal, but also larger particulate matter, including microbiota, is mobile in soil and potentially involved in matter interchange between surface and subsurface ecosystems. Specifically including the widely neglected particulate fractions, conditions and field-scale factors controlling the long-term seasonal and episodic dynamics of the “total mobile inventory” (Lehmann et al., 2021), in undisturbed soil and its translocation through the subsurface of the Critical Zone is almost unknown. To overcome this knowledge gap, we established long-term soil monitoring plots in the Hainich Critical Zone Exploratory (HCZE; NW-Thuringia, central Germany). Soil seepage from 22 tension-controlled lysimeters in topsoil and subsoil, covering different land use (forest, pasture, cropland) in the topographic recharge area of the HCZE, was collected and analyzed by a variety of analytical methods (physico-/chemical and spectroscopic) on a regular (biweekly) and event-scale cycle. Atmospheric forcing was found to be the major factor triggering the translocation of the mobile inventory, mainly causing considerable seasonality in the solute signature (e.g., sulphate) and seepage pH. However, episodic high-flow (infiltration) events rather than seasonality caused mobilization of significant amounts of particulates, for instance, after snow melts or rainstorms. Noteworthy, particulate organic carbon translocated during the winter-season infiltration events, accounted for up to 80% of annual fluxes. On average, 21% of the total OC of the seepage was particulate (>0.45 µm). Our study provides field-scale evidence for the importance of the mobile inventory fraction >0.45 µm for soil elemental dynamics and budgets. We, thus, suggest involving suspended fractions in environmental monitoring programs, although requiring adapted sampling procedures. References:Lehmann, K., Lehmann, R., & Totsche, K. U. (2021). Event-driven dynamics of the total mobile inventory in undisturbed soil account for significant fluxes of particulate organic carbon. Science of The Total Environment, 143774.

Drought and climatic change are among the main environmental stressors for the water and soil qualities. Soil water potential is the major soil-related factor controlling water availability to plants and their evapotranspiration. It consists of two main components: matric and osmotic potential. Although the effect of matric potential on plant evapotranspiration has been extensively studied under various conditions, there is still a lack of quantitative studies on the effects of osmotic potential on evapotranspiration.In our study, we investigated the influence of soil osmotic potential on the evapotranspiration rate and cumulative evapotranspiration of grass planted in small laboratory lysimeters. A sandy loam soil material was packed in four lysimeters with a volume of 6000 cm3 and equal bulk density. The soil material was air dried, freed from roots and passed through a 2 mm sieve. Each lysimeter was equipped with soil sensors at two different depths to monitor soil moisture, bulk electrical conductivity, temperature, and matric potential. To obtain continuous mass balance measurements, each lysimeter was placed on a balance connected to the computer. Grass seeds were planted in each lysimeter at the same density and irrigated with distilled water until plant height was 12 cm. Irrigation water of two different qualities (EC= 0 and 4.79 dS/m) was then applied to produce different levels (0 and -0.17 MPa) of osmotic potential. The volumetric water content was adjusted to a value between 15 and 20 % in each lysimeter during the grass growth period. When the volumetric water content reached 15 %, irrigation water was added to the lysimeters to increase it to 20 %. Data were collected to calculate changes in osmotic potential relative to changes in total soil water potential. In addition, the relationship between osmotic potential and evapotranspiration rate during the growing season was determined.Our results indicate a controlling role of soil osmotic potential on total soil water potential. This role results a significant reductions in evapotranspiration in response to increases in osmotic potential, in addition to effects on plant health. Osmotic potential has a significant function on total soil water potential when the soil becomes dry and poor water qualities are used in irrigation.

Source water apportionment studies using the dual isotopes of oxygen and hydrogen have revolutionized our understanding of ecohydrology. But despite these developments—mostly over the past decade—many technical problems still exist in terms of linking xylem water to its soil water and groundwater sources. This is mainly due to sampling issues and possible fractionation of xylem water. Here we explore whether or not leaf water alone can be used to quantify the blend of rainfall event inputs from which the leaf water originates. Leaf water has historically been avoided in plant water uptake studies due to the extreme fractionation processes at the leaf surface. In our proof of concept work we embrace those processes and use the well-known Craig and Gordon model to map leaf water back to its individual precipitation event water sources. We also employ a Bayesian uncertainty estimation approach to quantify source apportionment uncertainties. We show this using a controlled, vegetated lysimeter experiment where we were able to use leaf water to correctly identify the mean seasonal rainfall that was taken up by the plant, with an uncertainty typically within ±1‰ for δ18O. While not appropriate for all source water studies, this work shows that leaf water isotope composition may provide a new, relatively un-intrusive method for addressing questions about the plant water source.