Parameterisation of unsaturated flow models for estimating spatial-scale groundwater recharge is usually reliant on expert knowledge or best-estimated parameters rather than robust uncertainty analysis. This study chose the Campaspe catchment in southeastern Australia as a field example and examined the uncertainty of spatial groundwater recharge by performing uncertainty analysis. The study area was first divided into 13 zones according to different vegetation types, soil groups and precipitation. Individual models were then established for these zones using the biophysically based modelling code WAVES (Water Atmosphere Vegetation Energy and Solutes), which is capable of simulating unsaturated flow. The Monte Carlo method, together with the Latin-Hypercube sampling technique, was employed to perform uncertainty analysis by comparing modelled monthly evapotranspiration (ET) to MODIS ET. The results show that the common one-estimate-per-site approach can still identify the spatial pattern of groundwater recharge in the study area due to the presence of a precipitation pattern. In comparison, the uncertainty analysis not only identifies the spatial pattern, but also provides confidence levels in groundwater recharge that are critical for water resources management. The results also show that recharge absolute uncertainty is directly proportional to the amount of water input, but relative uncertainty in recharge is not. This study indicates that spatial recharge estimation without model calibration or knowledge of model uncertainty could be highly uncertain. MODIS ET can be used to reduce recharge uncertainty, but it is unlikely to lower the recharge uncertainty by a large extent because of the MODIS ET estimation error.

Limited scientific information has been published on the application of tools in the geographic information system (GIS) environment to understand factors that influence groundwater recharge. The objectives of the research reported here were to understand the spatial variability of factors that influence groundwater recharge using GIS, and to estimate the amount of groundwater recharge and its spatial distribution in Illala catchment, northern Ethiopia. Reconnaissance surveys coupled with satellite imagery were used to collect data related to water, dry-deposition and hydrogeology from the study catchment. The data analysis involved geo-statistics. The chloride mass balance (CMB) method was applied to estimate mean groundwater recharge. The study catchment is distinguished by a semi-arid climate (average aridity index value of 0.35) and it is dominated by limestone-shale-marl intercalation. Mean chloride concentration in rainwater ranges from 0.4 to 1.28 mg/L, while values in dry deposition vary from 1.78 to 1.82 mg/m². Groundwater and runoff chloride concentration ranges are 1.4–31.96 mg/L and 0.60–1.56 mg/L, respectively. Mean annual groundwater recharge estimated by the CMB method varies from 6.1 to 288.3 mm, and the mean groundwater recharge represents 11.7% of the 548 mm mean annual rainfall. The CMB-derived groundwater recharge estimation showed a nearly comparable value with the recharge estimated by other approaches. More effort should be made to boost groundwater recharge using various recharge enhancing techniques such as constructing artificial recharge wells and water harvesting structures, targeting areas with the lowest recharge.

Although water is scarce in most deserts of the world, the middle-latitude desert of Hunshandake, China, has abundant water resources, mainly groundwater. In this study, isotopic and hydrochemical compositions were investigated to understand the recharge of groundwater in this desert. The groundwaters are fresh and depleted in δ²H and δ¹⁸O, compared with modern precipitation, but have high values of tritium (5–25 TU), indicating that these groundwaters are likely less than 70 years old but not of meteoric origin. Clear differences were observed between the north and south parts of the desert. Groundwater in the northern part is characterized by lower landform elevation, lower ion concentrations, higher tritium contents, higher deuterium excess, and more depleted values of δ²H and δ¹⁸O than that in the southern part. This indicates a discrepancy between the topographic hydraulic gradient and the isotopic and hydrochemical gradients of groundwater in the desert. It also implies different water sources between the two areas. Combined analysis was further performed on natural waters from the Dali Basin and surrounding mountains. It indicated that groundwater in the north is mainly sourced from the Daxin’Anling Mountains, by leaking of the Xilamulan River water through a thick faulted aquifer. Groundwater in the south has two sources, the Yinshan Mountains and Daxing’Anlin Mountains. Therefore, modern focused recharge is more significant for groundwater recharge in the desert than the mechanisms of diffuse recharge. A conceptual model of groundwater recharge is proposed: the MTVG (mountain water – tectonic fault hydrology – unconfined vadose zone – groundwater) mechanism.

Understanding the impacts of managed abstraction and recharge, i.e. artificial regulation of groundwater, on flow dynamics contributes to water resources planning and effective management of river basins. Based on the hydrogeological conditions of the aquifer in the Tailan River Basin, northwestern China, a two-dimensional sand-tank physical model and the corresponding numerical model were conceptualized and developed to investigate the influence of such regulation on the moisture content, groundwater flow patterns, groundwater age, residence time distributions, and groundwater flow paths in the groundwater reservoir. Four scenarios were examined at laboratory scale. The results showed that groundwater flow was influenced significantly by artificial regulation and that the depth of influence greatly increased depending on the regulation modes. Abstraction mainly alters the groundwater flow paths and moisture content at the ground surface in the core area of the depression cone and reduces the groundwater age in the entire aquifer. Groundwater flow lines are gradually parted by artificial recharge at different depths. Groundwaters of different ages have different behavior under the different artificial recharge depths and artificial recharge modes. Saddle points (kind of stagnation points) appeared at different locations, which were highly dependent on the modes of artificial regulation. Some of the lessons learned, and some management strategies, are proposed based on the results. Despite the dimensionality and scale of the model adopted, resulting in a relatively very large capillarity zone unrepresentative of field conditions, these findings nonetheless have important implications for understanding groundwater flow dynamics impacted by highly intensive human activities.

The aquifer beneath Chengdu Plain is a main water resource for drinking and industry, which has severe groundwater nitrate contamination due to the shallow water table and intensive agricultural activities. The aim of this study is to estimate nitrogen loading to the aquifer and to predict nitrate concentration in groundwater in response to changes in land-use and agricultural practices, i.e. nitrogen fertilizer application, in ‘Jingyang region’ of the Chengdu Plain, one of the most developed agriculture areas in southwestern China. The framework utilized a geographic information system to account for the spatial and temporal distribution of on-ground nitrogen sources and corresponding loadings, and employed an export coefficient model to estimate the corresponding nitrogen loss. The simulation of nitrate fate and transport in the aquifer was conducted by developing a groundwater mass transport model using MODFLOW and MT3DMS. A number of predictive simulations for year 2026 were carried out to evaluate the impact of land-use and proposed future management options on controlling groundwater nitrate contamination. The results show that a nitrate plume would extend over most of the study area with some local areas having concentrations exceeding 20 mg L⁻¹ under the current setting and the scenario of increasing agricultural land use. Reduction in fertilizer application rates did mitigate nitrate contamination; however, this effect diminished with the expansion of agricultural land use. Land-use planning should consider the significant effects of agriculture to improve the quality of groundwater in the Chengdu Plain.

Change in groundwater level is predicted for a special site where transient natural factors affecting the groundwater level are mixed with very irregular anthropogenic influences. When there is not enough hydrogeological information about the area to be analyzed, an artificial neural network (ANN) is a powerful tool for groundwater level forecasting in highly irregular and uncertain groundwater systems. In this study, groundwater levels were predicted by using ANN models with input variables composed of one natural factor and two anthropogenic factors in Yangpyeong riverside area, South Korea. Complex and irregular change of the groundwater level was monitored due to the operation of a groundwater heat pump system and winter intensive pumping for water curtain cultivation (by which greenhouses are warmed). The prediction results showed good performance with root mean square errors of 3–6 cm when the average groundwater level is about 25.59 m, the correlation coefficient is >0.9 and the Nash–Sutcliffe efficiency is >0.75, indicating that the ANN models are well suited for assessing complex groundwater systems. Along with the prediction, an extraction method was devised to calculate contributions and relative impacts of the input variables in the time-series-based ANN models. As a result, it was proved that the river level dominantly affects the groundwater level fluctuation, and the contributions of each influencing factor were obtained reliably according to spatial distribution and temporal variance. This makes the scheme effective for managing and using groundwater resources with consideration of every crucial influencing factor of the groundwater level fluctuation.

This study investigates whether increased use of the Ostrom design principles could improve groundwater governance research. The principles relate to self-organizing governance systems of common-pool resources, which are more likely to be sustainable if all eight design principles—e.g. clear resource and user boundaries, collective-choice arrangements, monitoring, sanctions, conflict-resolution mechanisms—are present. Empirical studies have proven the relevance and effectiveness of the Ostrom design principles for a range of common-pool resources. However, the application of the design principles to groundwater has been limited. The South African institutional landscape was therefore chosen as a case study to investigate the relevance of the design principles. The case study involved (1) comparing the design principles with established global governance benchmarking criteria, (2) assessing how implementable the design principles would be in South Africa, and (3) comparing the aims of the design principles and the broad aims of groundwater governance in South Africa. It was found that the Ostrom design principles provide researchers with a common ‘language’ for learning about the specific issues of a particular setting, learning from experiments in that setting, and learning from the experience of others. The Ostrom design principles and associated adaptive management, social learning, use of the diagnostic approach, and more specific hydrogeological principles are not mutually exclusive and can be complimentary. The implementation of groundwater governance in South Africa has been poor and few Ostrom design principles have been adopted. More use of the Ostrom design principles could improve groundwater governance in South Africa and globally.

The main factors that cause land subsidence are groundwater withdrawal and the load of high-rise buildings. Previous studies on land subsidence caused by high-rise buildings have focused on small areas. Few scholars have proposed land subsidence models that combine the effects of groundwater withdrawal and high-rise building load at a regional scale. This work was based on Biot’s consolidation theory and the nonlinear rheology theory. The soil parameters were varied in accordance with the Kozeny-Carman equation and Duncan-Zhang nonlinear model, and applied to a site in eastern China. A three-dimensional finite element method (FEM) program, fully coupling varying soil parameter values and fluid-solid characteristics of land subsidence, was coded using FORTRAN. The program was used to simulate and predict regional land subsidence and to study the coupling effects of groundwater withdrawal and high-rise building load. The results showed that the soil parameters varied in reasonable range and the trend of variation was consistent with the characteristics of soil deformation. The sum of the land subsidence under high-rise building load alone and groundwater withdrawal alone differed from land subsidence under the combined effects of groundwater withdrawal and high-rise building load. The coupling effect of land subsidence caused by high-rise building load and groundwater withdrawal was shown to be nonlinear.

Shenzhen is the major financial and high-tech center in southern China. The megacity has grown rapidly in the last 40 years with the population increasing from about 30,000 in 1979 to 20 million in 2016. The study area (2,015 km²) is about 42% urban and 58% undeveloped land. The rapid development of the megacity has resulted in severe degradation of the groundwater and surface-water resources and has created a nearly insatiable demand for water, with an average consumption of 2000 × 10⁶ m³/year. Groundwater is an important component of the baseflow of the many streams in the area and is used for potable water supply and irrigation in some of the rural parts of the municipality. This study develops a conceptual model and quantitative framework for assessing the groundwater resources of Shenzhen. The groundwater system consists of shallow aquifers of alluvium and weathered bedrock overlying low permeability igneous and sedimentary rocks. The complex geologic setting was conceptualized as a block structure with blocks bounded by high-angle faults. The water budget in Shenzhen was quantified. The estimated average groundwater discharge is about 12% of annual precipitation. The study provides a starting point to investigate how a megacity such as Shenzhen should manage and protect its groundwater as a strategic resource and environmental asset. It is also a basic management tool for analyzing and contributing to urban drainage concepts such as the “sponge city”.