A hydrological study of four streambed recharge structures, locally called check dams, in a monsoonal area of hard-rock terrain in Rajasthan, India, was conducted over 3 years to evaluate their contribution to agricultural production. Their catchment area totalled 3,003 ha, and mean annual recharge from the 4 impoundments was 779,000 m³ or 26 mm. The calculated components of the annual water balance of these check dams are presented, together with a sensitivity analysis on unmeasured parameters and documentation of capital and maintenance costs of check dams. The maximum recharge was found to occur in the wettest year for the two structures on first-order streams; however, for the two structures on second-order streams, the maximum recharge occurred in the average rainfall year because, at these sites, groundwater levels rose so that the stream became hydraulically connected to the aquifer for a period in the wettest year causing mean dry weather infiltration rates to diminish. The study also evaluated the effect of manual desilting and mechanical desilting on mean dry-weather-infiltration rate. For the check dam that was manually desilted, the recharge increased by 84% over that of the preceding year, whereas for the mechanically desilted check dam it reduced by 18%, and the two control check dams increased by 13%. A present value analysis for net benefits of additional crop production attributable to recharge from check dams indicated that, after accounting for average annual maintenance costs 2.9% of capital costs, the benefit:cost ratio of the four check dams averaged 4.1. Hence this study shows that these check dams are economically attractive at the local level for securing irrigation water supplies.

Accurate characterization of aquifers remains challenging for large-scale systems because of the spatial heterogeneity of hydraulic properties and temporal variability of hydrologic inputs. This study highlights the importance of integrating geological, hydrogeological and geophysical approaches to characterize an aquifer and evaluate groundwater productivity. Data from geological maps, drill logs, a pumping test, vertical electrical soundings (VES) and different field hydrogeological studies were combined and applied to a heavily extracted aquifer system—Lake Haramaya watershed, Ethiopia. From the geological characterization, the aquifer was found to be a single heterogeneous and anisotropic unconfined unit. Significant differences were found between the three-dimensional geological models of the aquifer developed from the drill logs and VES data; the VES data were likely affected by moisture content. The pumping-test and VES data were combined to estimate transmissivity (T; 126.5 ± 25.8 m²/day) and hydraulic conductivity (K; 4.1 ± 1.0 m/day). This combined use allowed for a reduction in uncertainty (40.1% for T and 33.3% for K) compared with values estimated from the VES data alone. The combined approach also allowed for much greater spatial coverage and a higher resolution characterization of the aquifer. The available volume of groundwater resource in the system was estimated at ~0.62 ± 0.09 km³. The groundwater extraction rate was ~30,120 m³/day, approximately double the estimated sustainable yield of the aquifer (15,720 m³/day). This showed that the current exploitation rate could exhaust groundwater resources in 27–32 years and should be reduced by 50% to ensure sustainability of the groundwater resource.

Many coastal areas around the world suffer severe water stresses due to improper management of water resources. In these areas, groundwater is typically the most important source for drinking water, and its overexploitation may lead to deterioration in water quality. In coastal confined aquifers, the dynamics of saltwater intrusion (SWI) and well salinization are the focus of many recent studies that commonly do not include a geological study of the subsurface structure of the aquifer. The goal of the present work is to study the effect of groundwater extraction on SWI, using the Judea Group Aquifer as a case study representing a coastal confined aquifer that suffers drawdown due to excess pumping. First, the offshore-onshore structure of the aquifer is described, and then a groundwater model is constructed based on the inferred structure. The resulting model shows that under realistic conditions, a water well situated 5 km inland from the shoreline is expected to undergo salinization after ~190 years since level drop. The SWI advances inland faster when the confinement is efficient, suggesting that semi-confined aquifers should be preferred for pumping compared with confined ones. Additionally, the model shows that under certain conditions, deep submarine groundwater discharge (SGD) occurs through the aquifer outcrop, ~15 km offshore and at depths of ~200 m. The SGD comprises brackish and warm water. The insights from this work are important both for studies on freshwater budgets in coastal areas and for the study of SGD and its implications for the ocean.

Se ha estudiado el ciclo de vida durante un periodo anual (diciembre 2016–noviembre 2017) de los anfibios en dos cuerpos de agua artificiales en el límite oriental de la distribución de la especie amenazada Alytes dickhilleni Arntzen y García-París, 1995. En ambos sistemas, se reproduce la especie objetivo y dos más, Bufo spinosus Daudin, 1803, y Pelophylax perezi (LópezSeoane, 1885). Los ciclos reproductivos de A. dickhilleni y P. perezi muestran semejanzas con lo descrito en medios naturales y artificiales en la Región de Murcia; por el contrario, B. spinosus presentó un adelanto significativo. Este estudio pone de manifiesto el importante papel de los cuerpos de agua artificiales ligados a prácticas ganaderas tradicionales para la conservación de A. dickhilleni en el sureste ibérico semiárido. | Abstract: Life cycle of amphibian community inhabiting two artificial ponds on the eastern edge of the native distribution of the endangered species Alytes dickhilleni Arntzen and García- Paris, 1995, was studied over a complete annual cycle (from December 2016 to November 2017). We confirm the breeding status of the target species and two more, Bufo spinosus Daudin, 1803 and Pelophylax perezi (López-Seoane, 1885). Breeding cycles of A. dickhilleni and P. perezi showed similar phenology to available data from other natural and manmade ponds on Region of Murcia; conversely, B. spinosus showed a slightly advanced cycle. This study highlights the important role of artificial and traditional livestock ponds to conservation of A. dickhilleni population in Iberian southeast.

Este estudio presenta el componente ingenieril aplicado a una propuesta de aprovechamiento sostenible de agua lluvia para la zona de influencia del Humedal La Vaca definida en las 42 hectáreas de la infraestructura de la central de abastos de alimentos más grande de Colombia, esto como alternativa de suministro hídrico para jardines verticales y techos verdes. El proyecto busca promover un uso eficiente del recurso hídrico a partir de Sistemas Urbanos de Drenaje Sostenible (SUDS) que a su vez mitiguen el riesgo de inundación característico de la zona. | This study presents the engineering component applied to a proposal for sustainable use of rainwater for the area of influence of La Vaca wetland defined in the 42 hectares of the infrastructure of the largest food supply center in Colombia, this as an alternative supply water for vertical gardens and green roofs. The project seeks to promote the efficient use of water resources from Sustainable Urban Drainage Systems (SUDS) that in turn mitigate the flood risk characteristic of the area.

Saltwater intrusion is one of the most pressing environmental concerns in coastal areas with increased water demands. Water extraction decreases the level of fresh groundwater, reducing the water pressure and allowing saltwater to flow further inland. Tools for simulating, monitoring and managing saltwater intrusion can provide valuable support in decision-making for management options. In this work, such a tool was developed for the arid coastal aquifer of La Paz in Baja California, Mexico. A geomodel was generated by using a transient electromagnetic method (aquifer geometry, saltwater intrusion). This geomodel, in turn, was used to construct a three-dimensional density-dependent flow model to simulate groundwater flow and saltwater intrusion during the past decades. The results confirmed that a large cone of depression had formed due to excessive pumping in the agricultural area. This successively led to the inversion of the hydraulic gradient and seawater intrusion advancement on the order of 6–8 km inland in the northern-central portion of the aquifer. Freshwater recharge mostly originates from the mountainous southeastern portion of the basin. It supplies water for the city of La Paz and counteracts the saltwater intrusion advancement. The alternation of advancement and retreat of the freshwater–saltwater interface could be attributed to changing climate effects and/or policy changes.

A hydro-economic approach for planning on-farm managed aquifer recharge is developed and demonstrated for two contiguous sub-basins in California’s Central Valley, USA. The amount and timing of water potentially available for recharge is based on a reoperation study for a nearby surface-water reservoir. Privately owned cropland is intermittently used for recharge with payments to landowners that compensate for perceived risks to crop health and productivity. Using all cropland in the study area would have recharged approximately 4.8 km³ (3,900 thousand acre-feet) over the 20-year analysis period. Limits to recharge effectiveness are expected from (1) temporal variability in recharge water availability, (2) variations in infiltration rate and few high-infiltration recharge sites in the study area, and (3) recharged water escaping from the study area groundwater system to surface water and adjacent sub-basins. Depending on crop tolerance to ponding depth, these limitations might be reduced by (1) raising berm heights on higher-infiltration-rate croplands and (2) creating dedicated recharge facilities over high-infiltration-rate sites.

A significant volume of an aquifer along the coastline in the German Bight is salinized by seawater intrusion. The mean sea-level rise (MSLR) is expected to continue in the future due to global climatic change, subsequently degrading the fresh groundwater resources. To impede further salinization in the future, a solution is proposed based on weir construction in an existing canal hydraulically connected to the aquifer. The effect is twofold: (1) the elevated groundwater level can upgrade present fresh groundwater resources by shifting the saltwater–freshwater interface position further seaward, or by inhibiting its landward movement, and (2) the inland water level can be elevated, expanding surface water ponds. A fully coupled three-dimensional numerical surface-subsurface model (a modified HydroGeoSphere code) was used to simulate the effects of variable weir construction heights under different MSLR rates, and to quantify the gain of aquifer freshwater volume and loss of usable land due to surface ponding. Construction of a higher weir increases the desalinized aquifer volume and decreases the newly salinized aquifer volume under future MSLR. A minimum height of a weir was determined under a certain MSLR rate to maintain the present freshwater resource. Both weir construction and MSLR can cause the loss of land usage. Computed loss-gain ratio curves can be utilized to determine the optimal weir height, meeting the economic requirements of coastal land management under future MSLR.

Regional three-dimensional groundwater-flow and saltwater transport models were built to analyse saltwater intrusion in the Great Maputo area, southern Mozambique. Increased water demand has led to many private groundwater abstractions, as the local public water supply network has already reached maximum capacity. Pushing for new strategies to tackle the water-supply shortages exposes the aquifer system to saltwater intrusion from entrapped fossil saline groundwater and seawater. Previous attempts at modelling have been frustrated by data limitations. This study compiled all the available data to build the models, which were subsequently calibrated with observed heads, discharges and salt concentrations. The transport models were used to test hypotheses of potential sources of saltwater resulting in the current salinity distribution. Furthermore, scenarios were simulated to assess the impacts of sea-level rise and projected groundwater abstractions. Results show that saline groundwater is widely distributed in the aquifer’s western sector, where it is a limiting factor for groundwater development, and seawater intrusion is a risk along the coastline. Newly constructed wells (46) along the Infulene River can be operated with some impacts of saltwater upconing and must be closely monitored. Although current groundwater abstractions (60,340 m³/day) are still small compared with groundwater recharge (980,823 m³/day), larger volumes of abstraction are feasible only when using a high number of production wells further away from the city with relatively low yields to avoid saltwater upconing. Capture of fresh groundwater upstream of discharge areas by wells for water supply is possible while maintaining groundwater discharges for groundwater dependent ecosystems.

Groundwater plays a fundamental yet often little appreciated role in supporting economic development and human well-being in both urban and rural environments, as well as supporting many aquatic ecosystems in Africa. Thus, groundwater has high relevance to the development and well-being of Africa, if adequately assessed and sustainably exploited. Whilst the potential for groundwater-resources development continues to be reported in the literature, a quantitative understanding of these issues remains poor. The objective of this paper is to highlight the main groundwater issues and problems in Africa and the current and expected opportunities for sustainable groundwater management. This will be done through the review of existing knowledge of groundwater resources and of ongoing and planned groundwater management programs and initiatives. Groundwater resources in Africa face increasing threat of pollution from urbanisation, industrial development, agricultural and mining activities, and from poor sanitation practices and over-exploitation due to increasing demand to meet human and agricultural needs. However, despite the existence of a number of groundwater management challenges, groundwater resources in Africa are still generally under-developed and can meet the various needs in a sustainable manner if better managed. Thus, strategies to ensure sustainable development and management of groundwater resources need to be put in place. These include establishment of groundwater monitoring systems, understanding of the groundwater–aquatic ecosystem relationships, management of transboundary aquifers, addressing climate-change impacts on groundwater, assessing the impact of increased pumping from various types of aquifers on sustainability of groundwater abstraction, and capacity building in groundwater management.