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Consideration of regional groundwater flow in aquifer systems allows for solving groundwater issues on a larger scale than single aquifers and contributes to all practical aspects of the UN’s Sustainable Development Goals for water. The approach has been extended to a wide range of hydrogeological environments. However, it suffers from poorly constrained terminology and conceptualisation, compounded by the difficulties of interpreting complex groundwater flow systems. This essay aims to initiate a discussion on improving the application of regional groundwater flow approaches.

One of the most critical stages for developing groundwater resources for drinking water use is assessing the water quality. The use of a Water Quality Index (WQI) is considered an effective method of evaluating water quality. The objective of this research was to evaluate the performance of six multiple artificial intelligence techniques, i.e., linear regression (stepwise), support vector regression SVM (linear and polynomial kernels), Gaussian process regression (GPR), Fit binary tree, and artificial neural network ANN (Bayesian) to predict the WQI in Jizan, Southern Saudi Arabia. A total of 145 groundwater samples were collected from shallow dug wells and boreholes tapping the phreatic aquifer. The WQI was calculated from 11 physicochemical parameters (pH, TDS, Ca2+, Mg2+, Na+, K+, Cl−, SO42−, HCO3−, NO3−, and TH). The spatial distribution results showed that higher values of Cl− and SO42− were recorded in the places close to the coastline, indicating the occurrence of seawater intrusion and salinisation. Seven wells had a WQI of greater than 300, indicating that the water was unfit for consumption. The results showed that the GPR, linear regression (stepwise), and ANN models performed best during the training and testing stages, with a high correlation of 1.00 and low errors. The stepwise fitting model indicated that pH, K+, and NO3− were the most significant variables, while HCO3− was a non-significant variable for the WQI. The GPR, stepwise regression, and ANN models performed best during the training and testing stages, with a high correlation and low errors. In contrast, the SVM and Fit binary tree models performed the worst in the training and testing phases. Based on subset regression analysis, the optimum input combination for WQI model prediction was determined as these eight input combinations with high R2 (0.975–1.00) and high Adj-R2 (0.974–1.00). The resultant WQI model significantly contributes to sustainable groundwater resource management in arid areas and generates improved prediction precision with fewer input parameters.

The theory of regional groundwater flow is sixty years old in 2023, which has made it possible to evaluate groundwater flow systems and evolution in sedimentary basins. Recently, the approach has been extended to different environments in the Earth's crust. By applying regional groundwater flow theory, we can solve groundwater issues on a larger scale than for single aquifers. Application of the concept contributes to all practical aspects of groundwater topics, including the UN’s Sustainable Development Goals for water.However, the developed terms related to groundwater flow evaluation need to be more strictly defined and clarified for interpreting complex hydrogeological flow systems. The presentation summarizes the results of discussions among RGFC-IAH board members on this topic and tries to provide some necessary frameworks for the future application of the concept.At regional scales, groundwater flow evaluation should include the concept of aquifer systems. The term artesian basin has become obsolete because it implies impermeable layers in natural environments; groundwater basin is preferred instead. Sedimentary basin is a broader term which can contain more than one groundwater basin. For the goals of flow system evaluation, the term groundwater basins can be used, which are characterized by siliciclastic basin fill and basement aquifer systems. The full-groundwater basin is required for 2D and 3D interpretations, because half- (or symmetric-) basin assessment can provide misleading results. Hydraulic continuity is a fundamental principle in groundwater flow evaluation, it can be assumed in groundwater basins across multiple aquifers, aquitards and faults, as long as one has no contradicting evidence. Conceptual groundwater flow models need to be tested with specific field data, numerical simulations and groundwater flow-related manifestations.The presentation aims to initiate a discussion on improving the application of regional groundwater flow theory. The conference presentation is supported by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1- 21-2022-00014 project.

In the coming years, climate change is predicted to impact irrigation water demand considerably, particularly in semi-arid regions. The aim of this research is to investigate the expected adverse impacts of climate change on water irrigation management in Saudi Arabia. We focus on the influence of climate change on irrigation water requirements in the Al Quassim (97,408 ha) region. Different climate models were used for the intermediate emission SSP2-4.5 and the high emission SSP5-8.5 Coupled Model Intercomparison Project Phase 6 (CMIP6) scenarios. The FAO-CROPWAT 8.0 model was used to calculate reference evapotranspiration (ETo) using weather data from 13 stations from 1991 to 2020 and for both the SSP2-4.5 and SSP5-8.5 scenarios for the 2040s, 2060s, 2080s, and 2100s. The findings indicated that, for the 2100s, the SSP2-4.5 and SSP5-8.5 scenarios forecast annual average ETo increases of 0.35 mm/d (6%) and 0.7 mm/d (12.0%), respectively. Net irrigation water requirement (NIWR) and growth of irrigation water requirement (GIWR) for the main crops in the Al Quassim region were assessed for the current, SSP2-4.5, and SSP5-8.5 scenarios. For SSP5-8.5, the GIWR for the 2040s, 2060s, 2080s, and 2100s are expected to increase by 2.7, 6.5, 8.5, and 12.4%, respectively, compared to the current scenario (1584.7 million m3). As a result, there will be higher deficits in 2100 under SSP5-8.5 for major crops, with deficits of 15.1%, 10.7%, 8.3%, 13.9%, and 10.7% in the crop areas of wheat, clover, maize, other vegetables, and dates, respectively. Optimal irrigation planning, crop pattern selection, and modern irrigation technologies, combined with the proposed NIWR values, can support water resources management. The findings can assist managers and policymakers in better identifying adaptation strategies for areas with similar climates.

A fixed climatological year is generally used to determine rainy season onset and cessation. However, due to changes in climate, the fixed climatological year might not be the right basis for the onset and cessation dates estimation. This study proposes the usage of the driest period in the year to establish a flexible climatological year to determine rainy season onset and cessation dates. The driest period of a climatological year is defined as the period of 14 consecutive days, which has the lowest accumulated precipitation. The flexible climatological year begins on the first day of the driest period and ends before the driest period of next year. The onset and cessation dates resulting using this new flexible climatological year are compared against those resulting from the traditional approach. Three onset estimation methods were selected for demonstration of the method: agronomy, anomalous accumulation, and a modified local method. The results showed that overall, the three methods produced similar onsets for both types of climatological years. However, the use of a flexible year showed clear advantages in the application of anomalous accumulation for large and heterogeneous climatic zones because it helped to set a start date and an average daily precipitation, which improved the onset and cessation date calculations.

Refereed/Peer-reviewed Groundwater dependent ecosystems (GDEs) are vulnerable to groundwater regime changes. However, their protection is often hampered by challenges in their identification. Within is presented a remote sensing-based GDE potential mapping approach based on the persistency of relevant vegetation parameters during prolonged dry periods as an indicator of potential ‘consistency’ of water supply (e.g. groundwater). The study uses a novel approach to characterising persistency for selected vegetation parameters based on a normalised difference measure and an adaptation of the coefficient of variation statistic. Aggregation of parameters was facilitated through the analytic hierarchy process providing a structured weighting approach to minimise parameter bias. The approach is demonstrated in the semi-arid Flinders Ranges of South Australia where new groundwater resources are being sought to support local domestic and industry needs. Variations in GDE potential were mapped to better target areas where exploration of groundwater should be avoided. Mapping results indicated a high-level of agreement of 77% with an independent springs dataset, along with an 87% agreement with areas coinciding with known phreatophyte species and depths to groundwater. The index-based mapping approach has potential applicability across landscapes, as it normalises for variations in vegetation cover, minimises technical overheads, and employs continental-wide remote sensing data-products.

The lowland floodplains of the Lao People’s Democratic Republic (PDR) experience prolonged dry seasons characterized by pronounced and common water scarcity, with water supplies increasingly offset with groundwater. Groundwater assessment is still at a very rudimentary stage in Laos, making it difficult to ensure that new water supplies are developed successfully and managed sustainably. The goal of this study is to apply a variety of field hydrogeophysical techniques to this problem and in the process help build and strengthen human and institutional capacity with various stakeholder groups from the government, the university, and the community. The study area focuses on a cross section of the Vientiane Plain (VP) in the Lower Mekong Basin in central Lao PDR to identify and characterize the hydrogeology and groundwater quality. The research collaboration has built and strengthened stakeholder capacity by developing and progressing the hydrogeologic field mapping of the VP. It has provided local undergraduate and postgraduate training opportunities using several different near-surface geophysical and hydrogeologic techniques, some previously untested in Lao PDR. At one of the survey sites, the geophysics has indicated the spatial extent of the shallow aquifer and in the process identified an extensive conductive zone, interpreted as more saline groundwater. Any groundwater development within this or similar zones is likely to be unsuitable as sources for drinking and irrigation water. Engagement with the local village authorities has supported local community members and government to expand groundwater development for rural water supplies. Access to groundwater as a reliable, safe, and secure resource provides an opportunity for strengthening the resilience of farmers to changing climatic conditions. Participatory research collaboration of this kind can positively enhance data and build capacity, which is a required precursor for improving knowledge and management of poorly understood groundwater resources.

This study evaluates the potential of kriging-based (kriging and kriging-logistic) and machine learning models (MARS, GBRT, and ANN) in predicting the effluent arsenic concentration of a wastewater treatment plant. Two distinct input combination scenarios were established, using seven quantitative and qualitative independent influent variables. In the first scenario, all of the seven independent variables were taken into account for constructing the data-driven models. For the second input scenario, the forward selection k-fold cross-validation method was employed to select effective explanatory influent parameters. The results obtained from both input scenarios show that the kriging-logistic and machine learning models are effective and robust. However, using the feature selection procedure in the second scenario not only made the architecture of the model simpler and more effective, but also enhanced the performance of the developed models (e.g., around 7.8% performance enhancement of the RMSE). Although the standard kriging method provided the least good predictive results (RMSE = 0.18 ug/l and NSE=0.75), it was revealed that the kriging-logistic method gave the best performance among the applied models (RMSE = 0.11 ug/l and NSE=0.90).

Yolŋu Aboriginal people’s knowledge about water (“gapu”) and its governance has strong cultural significance and meaning in East Arnhem Land Aboriginal worlds in northern Australia. This study used...

Adolf and Günther Thiem, father and son, left behind a methodological legacy that many current hydrogeologists are probably unaware of. It goes far beyond the Dupuit–Thiem analytical model for pump test analysis, which is connected to their name. Methods, which we use on a day-to-day basis today, such as isopotential maps, tracer tests, and vertical wells, were amongst the many contributions which the Thiems either developed or improved. Remarkably, this was not done in a university context but rather as a by-product of their practical work of designing and building water supply schemes in countries all over Europe. Some of these waterworks are still active. Both Thiems were also great science communicators. Their contributions were read and applied in many countries, especially in the USA, through a personal connection between Günther Thiem and Oscar Edward Meinzer, the leading United States Geological Survey (USGS) hydrogeologist of the time.

For more than a century, the strong advice in geology has been to rely on multiple working hypotheses. However, in groundwater research, as supported by modelling, often a stepwise approach with respect to complexity is promoted and preferred by many. Defining a hypothesis, let alone multiple hypotheses, and testing these via groundwater models is rarely applied. The so-called ‘conceptual model’ is generally considered the starting point of our beloved modelling method. A conceptual model summarises our current knowledge about a groundwater system, describing the hydrogeology and the dominating processes. Conceptual model development should involve formulating hypotheses and leading to choices in the modelling that steer the model predictions. As many conceptual models can explain the available data, multiple hypotheses allow assessing the conceptual or structural uncertainty.This presentation aims to review some of the key ideas of 125 years of research on (not) handling conceptual hydrogeological uncertainty, identify current approaches, unify scattered insights, and develop a systematic methodology of hydrogeological conceptual model development and testing. We advocate for a systematic model development approach based on mutually exclusive, collectively exhaustive range of hypotheses, although this is not fully achievable. We provide examples of this approach and the consequential model testing. It is argued that following this scientific recipe of refuting alternative models; we will increase the learnings of our research, reduce the risk of conceptual surprises and improve the robustness of the groundwater assessments. We conclude that acknowledging and explicitly accounting for conceptual uncertainty goes a long way in producing more reproducible groundwater research. Hypothesis testing is essential to increase system understanding by analyzing and refuting alternative conceptual models. It also provides more confidence in groundwater model predictions leading to improved groundwater management, which is more important than ever.

Climate change has a significant impact on the environment by increasing the frequency of extreme precipitation events. Underestimating the potential risks of such events and lack of climate resilience will result in a substantial crisis in terms of water security. Understanding the hydrological consequences is difficult due to complexities and additional environmental feedbacks, depending on landuse/landcover, soil and climate.The Gravity Recovery and Climate Experiment (GRACE) has provided an unprecedented perspective on global fluctuations in terrestrial water storage (TWS) over the past decade. While numerous studies have correlated different hydrological variables against TWS, no study has tested different rainfall thresholds (intensity) impacting TWS. Existing studies mostly have explored the relationship between TWS anomalies and hydrological variables using individual responses, while few have looked at multi-variable interaction. Single indicators (e.g., standardized precipitation index) may limit ecohydrological understanding of soil-vegetation-atmosphere water transfer, as many factors play essential roles in land-atmosphere interactions. In particular, rainfall characteristics can significantly impact the interaction between hydrological factors by accelerating or slowing processes. Hence, including appropriate temporal resolution of precipitation in analyses is essential; e.g., monthly data are not a good indicator for understanding ecohydrological interactions. Therefore, this research aims to improve our understanding of the spatiotemporal response of TWS to climate change impacts on rainfall characteristics. Monthly GRACE TWS time series anomalies are analyzed against aggregated monthly rainfall with different daily thresholds (intensities). The obtained results are used to find explanatory variables such as land use/land cover, soil type, and climatic zones that determine the significance between TWS and various variables. The methodology provides a valuable insight into the mechanisms in which TWS is affected by rainfall characteristics at different spatiotemporal scales across various hydrological contexts across Australia.

Despite the potential of remote sensing for monitoring reservoir operation, few studies have investigated the extent to which reservoir releases can be inferred across different spatial and temporal scales. Through evaluating 21 reservoirs in the highly regulated Greater Mekong region, remote sensing imagery was found to be useful in estimating daily storage volumes for within-year and over-year reservoirs (correlation coefficients [CC] ≥ 0.9, normalized root mean squared error [NRMSE] ≤ 31%), but not for run-of-river reservoirs (CC

Identifying and quantifying recharge processes linked to ephemeral surface water features is challenging due to their episodic nature. We use a combination of well-established near-surface geophysical methods to provide evidence of a surface and groundwater connection under a small ephemeral recharge feature in a flat, semi-arid region near Adelaide, Australia. We use a seismic survey to obtain P-wave velocity through travel-time tomography and S-wave velocity through the multichannel analysis of surface waves. The ratios between P-wave and S-wave velocities are used to calculate Poisson's ratio, which allow us to infer the position of the water table. Separate geophysical surveys were used to obtain electrical conductivity measurements from time-domain electromagnetics and water contents from downhole nuclear magnetic resonance. The geophysical observations provide evidence to support a groundwater mound underneath a subtle ephemeral surface water feature. Our results suggest that recharge is localized and that small-scale ephemeral features may play an important role in groundwater recharge. Furthermore, we show that a combined geophysical approach can provide a perspective that helps shape the hydrogeological conceptualization of a semi-arid region.

Adolf and Günther Thiem, father and son, left behind a methodological legacy that many current hydrogeologists are probably unaware of. It goes much beyond the Dupuit-Thiem analytical model for pump test analysis, which is connected to their name. Methods, which we use on a day-to-day basis today, such as isopotential maps, tracer tests and vertical wells were amongst the many contributions which the Thiems either developed or improved. Remarkably, this was not done in a university context but rather as a by-product of their practical work designing and building water supply schemes in countries all over Europe. Some of these water works are still active. Both Thiems were also great science communicators. Their contributions were read and applied in many countries, especially in the US, through a personal connection between Günther and O.E. Meinzer, the leading USGS hydrogeologist of the time.

Lao PDR is a poorly developed country, with a large rural population which relies heavily on agricultural production. The Vientiane Plain is one of the most important and largest agricultural produ...

Large-scale drought and wet phases, via ecosystem responses, can significantly influence the global atmospheric carbon budget. Australian landscapes, dominated by arid and semi-arid rangelands, play an important role in this regard. In this study, temporal variation of monthly Normalised Difference Vegetation Index (NDVI) of two rangelands with different grazing intensity were analysed against monthly precipitation and Gravity Recovery and Climate Experiment (GRACE) total water storage (TWS). The results show that regardless grazing regime, over 55% temporal variation of monthly NDVI anomaly can be explained by structured cumulative antecedent precipitation. It appears that the antecedent precipitation forms better predictor variables than GRACE TWS for this study area. The results also show that both grazing and drought reduce vegetation cover, and its response to precipitation. Drought exacerbates the grazing impact on NDVI-precipitation response. These results imply that grazing in arid and semi-arid rangelands can reduce the capacity of ecosystems to assimilate atmospheric CO2 during wet years and episodic wet events. It is important to incorporate temporal structures of intra- and inter-annual antecedent precipitation in investigating vegetation dynamic responses to precipitation. By doing so, it is possible to predict monthly vegetation dynamics to support grazing management.

© 2018 Elsevier BV. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (December 2018) in accordance with the publisher’s archiving policy, Hydrogeological conceptual models are collections of hypotheses describing the understanding of groundwater systems and they are considered one of the major sources of uncertainty in groundwater flow and transport modelling. A common method for characterizing the conceptual uncertainty is the multi-model approach, where alternative plausible conceptual models are developed and evaluated. This review aims to give an overview of how multiple alternative models have been developed, tested and used for predictions in the multi-model approach in international literature and to identify the remaining challenges. The review shows that only a few guidelines for developing the multiple conceptual models exist, and these are rarely followed. The challenge of generating a mutually exclusive and collectively exhaustive range of plausible models is yet to be solved. Regarding conceptual model testing, the reviewed studies show that a challenge remains in finding data that is both suitable to discriminate between conceptual models and relevant to the model objective. We argue that there is a need for a systematic approach to conceptual model building where all aspects of conceptualization relevant to the study objective are covered. For each conceptual issue identified, alternative models representing hypotheses that are mutually exclusive should be defined. Using a systematic, hypothesis based approach increases the transparency in the modelling workflow and therefore the confidence in the final model predictions, while also anticipating conceptual surprises. While the focus of this review is on hydrogeological applications, the concepts and challenges concerning model building and testing are applicable to spatio-temporal dynamical environmental systems models in general.

This study presents a spatially explicit sensitivity and uncertainty analysis approach to a GIS-based multi-criteria groundwater potential zone model. The study addressed a deficiency in the way groundwater potential mapping results are typically presented using discrete class outputs without assessment of their certainty with respect to variations in criteria weighting, one of the main contributors to output uncertainty in GIS-based multi-criteria decision analysis studies. We argue, moderating groundwater potential mapping results with localised uncertainty levels will help to refine and prioritise groundwater exploration efforts. The approach also enables a better understanding of the underlying factors influencing uncertainty in model outputs, which can help to inform the calibration of input parameters to improve model performance. Although the procedures presented in this study have been applied to other types of multi-criteria evaluations, its integration in GIS-based groundwater potential modelling has received little attention. We provide a case study focused on a fractured rock environment surrounding the township of Hawker in South Australia where new groundwater resources are sought. Small incremental weight changes were applied one-at-a-time and automated as a task in ArcGIS Pro, built using the ArcPy Python module that interacts with spatial tools allowing geographical analysis. The approach is applicable to both continuous and discrete class-based mapping outputs and enabled a deeper understanding of model output behaviour with respect to criteria weighting alternatives. The case study findings demonstrate the potential value of the approach in mitigating uncertainty and improving confidence in locating sites with high groundwater potential. Refereed/Peer-reviewed

This study identifies which factor, increased atmospheric CO2 concentration or local moisture deficit, dominates the temporal occurrence of hot extremes at the global scale. The wavelet decomposed GRACE Terrestrial Water Storage (TWS) is for the first time applied in examining the relationship between soil moisture (θ) and number of hot days in the hottest month (NHD). It reveals stronger θ–NHD relationships over larger areas than other commonly used soil moisture proxies (i.e., standardized precipitation index (SPI) and model derived product). During the study period 1985–2015, hot extreme occurrence with a dominant influence from increased atmospheric CO2 concentration is mainly observed in South America, Africa and Asia, while soil moisture deficit dominates the occurrence of hot extremes in larger areas, including parts of North America, West Europe, Australia, Southeast Asia and South Africa. Global action in reducing emissions will support combating hot extremes. In addition, important attention should be directed to address, e.g. by adaptive land management, the increasing moisture deficit in some regions.

Study region The ungauged, agriculturally dominated La Vi River Basin, Vietnam. Study focus Groundwater abstraction for food and industrial production is increasing globally, putting pressure on groundwater resources and associated ecosystems. In many countries, monitoring of abstraction is poorly organised, resulting in a paucity of data, particularly in developing regions. Therefore, alternative approaches to estimate groundwater withdrawals are necessary. In this study, two soft-data approaches for indirect catchment-scale groundwater abstraction estimation are developed using: (1) local knowledge through a qualitative field survey of groundwater level fluctuations and groundwater withdrawals, and (2) land use data combined with local knowledge on cropping and irrigation practices. New hydrological insights for the region The approaches are tested and applied for the La Vi River Basin, for the 2016 dry season. Total dry season estimated abstractions of 31.07 × 106 m3 and 36.19 × 106 m3 resulted from the two approaches. The advantage of the second approach is the spatial distribution of the estimated groundwater abstraction, aligning highly intensive abstractions with intensive agricultural areas. Despite high uncertainty in both estimates, this quantitative estimate gives valuable information for water managers, and the relatively good agreement between the methods provides trust in the estimates. The approaches are cost-effective and computationally simple solutions for estimating groundwater abstraction in data-poor regions.

Simple analytical and numerical solutions for confined and unconfined groundwater-surface water interaction in one and two dimensions were developed in the STRIVE package (stream river ecosystem) as part of FEMME (flexible environment for mathematically modelling the environment). Analytical and numerical solutions for interaction between one-dimensional confined and unconfined aquifers and rivers were used to study the effects of a 0.5 m sudden rise in the river water level for 24 h. Furthermore, a two-dimensional groundwater model for an unconfined aquifer was developed and coupled with a one-dimensional hydrodynamic model. This model was applied on a 1 km long reach of the Aa River, Belgium. Two different types of river water level conditions were tested. A MODFLOW model was set up for these different types of water level condition in order to compare the results with the models implemented in STRIVE. The results of the analytical solutions for confined and unconfined aquifers were in good agreement with the numerical results. The results of the two-dimensional groundwater model developed in STRIVE also showed that there is a good agreement with the MODFLOW solutions. It is concluded that the facilities of STRIVE can be used to improve the understanding of groundwater-surface water interaction and to couple the groundwater module with other modules developed for STRIVE. With these new models STRIVE proves to be a powerful example as a development and testing environment for integrated water modeling.

Groundwater is the primary source of freshwater supply on remote small islands, where it exists as a freshwater lens. It is extremely vulnerable to over-extraction, pollution and seawater intrusion. Ensuring long-term sustainable management of the groundwater resource is of the utmost importance when there are growing water demands, sea-level rise and/or recharge decline. This study used a three-dimensional, variable-density numerical groundwater flow and solute transport model to investigate vulnerability of a freshwater lens in a multi-layered aquifer system on Milingimbi Island, a small tropical island in northern Australia. The model was used to explore the impacts and possibility of increased groundwater demand on the freshwater lens, its volume, geometry as well as the thickness of the transition zone. The risks of saltwater intrusion, both laterally from the ocean and by localised up-coning from the deeper, more saline aquifers beneath the freshwater lens, were also assessed. Model calibration used observed hydraulic heads and salinity observations from pumping and observation wells. Subsurface bulk conductivity values, which were calculated from inverted airborne electromagnetic (AEM) and near-surface geophysical data, were also used in the calibration process. The results showed that the hydraulic heads and observed salinity achieved the ‘best fit’ in the calibration process, whereas the addition of the geophysical data assisted in constraining the lens geometry in the steady state model and integrated the data poor areas based on traditional hydrogeological datasets. The models’ calibration sensitivity to the range of measured salinities could be enhanced by improving the conversion factor between the AEM-derived conductivity values and the observed salinity data. This would best be accomplished by targeted monitoring wells at discrete depths and locations across the lens and improvements in the sampling/restoration of existing ones. The numerical model provided a framework to evaluate the key underlying hydrogeological processes on the island, as well as an important decision-making tool to ensure a sustainable and reliable water supply for the island community.

More than half of the world’s population are urban dwellers, and this percentage is on the rise. Therefore, understanding the links between water, energy, and food requirements of cities plays a critical role in determining global resource consumption. Adelaide is a mid-size, coastal Australian city in Australia with a population of almost 1.3 million inhabitants. With its plentiful access to wind and solar energy, the Adelaide region has one of the highest rates of renewable energy production in the world, and access to additional, conventional energies supplies from other parts of the Australian network. However, the water supplies in this region are theoretically limited, as groundwater depletion is already occurring in the food production areas surrounding the city, and municipal water supplies rely heavily on the fully allocated Murray River system. Therefore, optimization of the food, energy and water requirements of the city provides an opportunity for optimal use of valuable resources. Quantification of these industries was not trivial and provided data availability and comparison challenges. Lessons learned on a quantitative example of the water-energy-food nexus at city scale are presented.

In many parts of the world, groundwater extraction for agriculture is strongly increasing, causing severe stress on groundwater resources and associated ecosystems. Understanding how groundwater flow systems support extractions is therefore essential. However, particularly in developing, rural, tropical regions, monitoring of groundwater levels, chemistry and extractions is poorly regulated, resulting in a lack of data. Hence, alternative approaches are necessary to develop best management practices in these groundwater basins. In this study, catchment-scale groundwater extraction is indirectly estimated by two “soft data” approaches: (1) using local knowledge through a qualitative field survey of groundwater level fluctuations and groundwater withdrawals; and (2) land-use/population data combined with local knowledge on cropping/water use practices. Spatially distributed recharge is simulated on the basis of a monthly water balance model, which requires widely available topographic, soil, land-use and meteorological data. Extractions and recharge force a simple, basin-scale groundwater model for assessment of impact of irrigation practices. Agricultural scenarios are developed and modelling procedures are designed to test the temporal and spatial vulnerability over a 100 yr time span of the groundwater resource. The approaches are tested and applied for the agricultural La Vi River basin, Vietnam, where the livelihood of the local farmers requires development of new agricultural and hydrological techniques. The typical cash-crops are cultivated on sandy soils and irrigated in the dry season from thousands of private shallow wells. The tropical climate and strong seasonal rainfall pattern produces a strong fluctuation in groundwater levels. The modelling shows significant spatio-temporal unmet pumping demand dependent on the agricultural development scenario, indicating the need and opportunity for planning of groundwater based irrigation development. Overall, the multi-method comprehensive approach supports basin-scale sustainable groundwater resource development and only requires relatively easily accessible data.

Understanding the mechanisms and controls on contaminant removal in streams is essential in managing human and ecosystem health. The hyporheic zone (HZ) plays a key role in the removal of contamina ...

Urbanization increases land surface temperature (LST) due to urban surfaces radiating heat, which is influenced by variations in building materials, heights and spacing, and street geometry amongst other natural and manmade factors [1]. LST increases water consumption especially in summer, due to human behavior such as increased showering, drinking, entertainment and cooling. This research aims to use thermal remote sensing data and GIS tools to quantify the impact of LST on water consumption (WC) for the different seasons in Khan Younis Governorate, Palestine. Correlation was studied between water meter data for 2017 (28,000 houses) and the corresponding LST data of Landsat 8 at 100 m resolution. This study shows the potential of remotely sensed LST datasets for estimating WC under various seasonal climatic conditions, which has the potential to be a valuable tool for the management of water resources in urban areas.

Australia, the driest inhabited continent, is prone to natural disasters, such as droughts, floods, bushfires, and heatwaves. Strong climate variability causes recurring threats to water supply, agriculture, and the environment. Improving our insight into changes in hydroclimatic patterns is required to provide useful information for society. Previous studies mainly focused on the causes of extreme wet or dry events in specific periods and their impacts on agriculture and ecosystems. An understanding of long‐term spatio‐temporal patterns of wetting and drying in Australia is still lacking. Here we show, based on analyses of Gravity Recovery and Climate Experiment satellite derived terrestrial water storage and extended datasets, that there are four consecutive periods of seesaw wetting and drying between eastern and western Australia in the past five decades. The seesaw phenomenon is characterized by eastern Australia gaining water, while western Australia is losing water, and vice versa. Strong La Niña induced continent‐wide wetting, resets this pattern, leaving each seesaw to last for 11 ± 5 years. We provide one possible mechanism related to vegetation response to climate variability and its feedback on hydrological processes to explain the seesaw pattern. The identified recurring seesaw pattern indicates that society would need to become more adaptive in managing forest, water, and disaster risks in the wake of a next strong La Niña induced continent‐wide wetting in Australia.

Identifying and quantifying recharge processes linked to ephemeral surface water features is challenging due to their episodic nature. We use a unique combination of well-established near-surface geophysical methods to provide evidence of a surface and groundwater connection under a small ephemeral recharge feature in a flat, semi-arid region near Adelaide, Australia. We use a seismic survey to obtain P-wave velocity through travel-time tomography and S-wave velocity through the multichannel analysis of surface waves. The ratios between P-wave and S-wave velocities allow us to infer the position of the water table. A separate survey was used to obtain electrical conductivity measurements from time-domain electromagnetics and water contents were acquired by downhole nuclear magnetic resonance. The combined geophysical observations provide evidence to support a groundwater mound underneath a subtle ephemeral feature. Our results suggest that recharge is localized and that small-scale ephemeral features play an important role in groundwater recharge. Furthermore, we show that a combined geophysical approach can provide a unique perspective that helps shape the hydrogeological conceptualization of a semi-arid region.

Appropriate land management can be an effective approach to improving water quantity regulation. There is, however, a need to identify both where measures are most needed and where they may be most effective. The water retention index (WRI) was developed with this goal in mind. The WRI is a composite indicator which takes into account parameters reflecting potential water retention in vegetation, water bodies, soil and underlying aquifers, as well as the influence of slope and artificially sealed areas. Three land management scenarios were simulated up to 2030 using the LUISA modeling platform: increasing grassland in upstream areas as well as afforestation in both upstream areas and riparian zones. The WRI was computed for all scenarios as well as a comparative “business†as†usual†baseline scenario. All scenarios showed an overall improvement of the index as compared to this baseline, with afforestation in upstream areas having the greatest effect. The WRI can provide useful insights into the current capacity of a landscape to regulate water as well as the effectiveness of possible remediation strategies applied at the European scale.

Intense deforestation over large areas is an important component of global models which aim to quantify the transfer of terrestrial siliceous material from the continent to the coast. Hence, there is a need for improved understanding of land use impact on Si export. We present a model that simulates the kinetic dissolution of biogenic Si in a forest soil. A kinetic equation was calibrated based on leaching experiments of soil columns at constant water flux. The calibrated equation was then used to simulate the Si export from a forest soil under varying atmospheric conditions and provided realistic Si concentrations in soil water. The same model was used to simulate the impact of reduced evapotranspiration due to deforestation and consequently increased soil water fluxes on the Si export. Results showed that lower amounts of biogenic silicon dissolved and higher Si fluxes were released to the system once water flux increased. The use of the kinetic dissolution equation for biogenic Si improves our understanding and the modelling of the Si release from soils towards the hydrographic system.

Spatial and temporal droughts during rainy seasons are important climatic aspects to consider in water resources management. The dry spell index, a time-independent index that considers the characteristic of dry days, dry spell, seasonal length and evaporation rate in drought severity estimation, is supporting the analyses of the spatiotemporal variations of drought severity in the rainy season of the Indonesian Maritime Continent (IMC) between 1998 and 2018. The rainy season was determined using a modified anomalous accumulation. The results showed that an increase in dry spells produced a consistently increasing temporal drought during the rainy season across the IMC. Meanwhile, spatial variation suggested that although there is an increase in the rainy season total accumulated precipitation and duration, a large area within the monsoon regime also experiences increased drought severity, indicating more frequent extreme precipitation. Regional drought severity was classified as normal with a tendency of an increasing area under dry categories. Overall, the rainy season drought has increased in the IMC from 1998 to 2018, elevating the threats of reduced agricultural production.

Among the advances made in analytical and numerical analysis methods to quantify groundwater/surface-water interaction, one methodology that stands out is the use of heat as an environmental tracer. A large data set of river and riverbed temperature profiles from the Aa River in Belgium has been used to examine the spatial-temporal variations of groundwater/surface-water interaction. Exchange fluxes were calculated with the numerical heat-transport code STRIVE. The code was applied in transient mode to overcome previous limitations of steady-state analysis, and allowed for the calculation of model quality. In autumn and winter the mean exchange fluxes reached −90 mm d−1, while in spring and early summer fluxes were −42 mm d−1. Predominantly gaining conditions occurred along the river reach; however, in a few areas the direction of flow changed in time. The river banks showed elevated fluxes up to a factor of 3 compared to the center of the river. Higher fluxes were detected in the upstream section of the reach. Due to the influence of exchange fluxes along the river banks, larger temporal variations were found in the downstream section. The exchange fluxes at the river banks seemed more driven by variable local exchange flows, while the center of the river was dominated by deep and steady regional groundwater flows. These spatial and temporal differences in groundwater/surface-water exchange show the importance of long-term investigations on the driving forces of hyporheic processes across different scales.