Abstract: Vietnam is a country with a long coastline and a high population density residing in the coastal plains. The largest dry area in Vietnam, the coastal plain of Ninh Thuan province, always lacks water in the first dry months of the year (Jan., Feb., Mar., and Apr.). Groundwater is an extremely valuable resource for supplies at this time. Therefore, the objective of this study is to establish a comprehensive approach to sustainable groundwater management in this semi-arid region. This approach is not only mitigating the negative impacts of factors such as climate change, sea level rise, and socio-economic development but also suggesting measures for management of aquifer recharge. A groundwater model for a 3-layer system with variable density flow SEAWAT is built to predict the impacts of climate change and sea level rise without a change in groundwater abstraction. This model helps to understand the trend of salt intrusion and lowering groundwater level in the study area. Afterwards, scenarios with different ground water abstraction and groundwater development such as ground dam, infiltration basin have been set up to meet the demands of socio-economic development in the future. Predicted results will show the impacts of the groundwater systems in the area such as groundwater level change, and saltwater intrusion. Controlled groundwater abstraction and some measures of groundwater development such as infiltration basin, underground dam would allow for an increase of up to 50000m3/day in the year 2050 without negative impacts on the aquifer system.

Abstract: Competing commercial demands on water resources need to be balanced as the world’s population rises. Generally, groundwater is raised by subsurface dams. In this paper, the geographic information system (GIS) software and a decision-making method were applied. As the first step, the limitations that affect the establishment of the subsurface dam were identified using eliminating criteria by the Boolean logic. Regarding the second step, the most appropriate axis was determined for subsurface dam construction in each of the limits. The analytical hierarchy process (AHP) was applied according to the evaluation criteria in this study. The aim of using AHP was to weigh and prioritize the criteria of the groundwater dam for recognizing appropriate sites. Among various places and regarding the subsurface dam construction, AHP was conducted using a hierarchy process for finding the most suitable sites in the third stage of the decision-making method. Finally, among the ten appropriate sites, cross comparison was drawn by using Decision Expert (DEX), Evaluation based on Distance from Average Solution (EDAS), and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Compared together (as a process of decision-making), DEX, TOPSIS, and EDAS methods assisted in ranking the most appropriate sites in the final step of subsurface dam pre-selection. A and C axes obtained scores between 1 and 2, among 10 axes according to the numerically ranked locations. Regarding the water shortage issue and better management of the underground water at certain levels, the findings of this study could be useful for the residents of Kajbid-Balaqly Watershed in the dry season. Further, water managers can use the above-mentioned methods for their decisions regarding the proper subsurface dam establishment.

Abstract: The Qanat water systems (QWSs), the ancient water engineering systems in Iran belonging to the very distant past, have harvested groundwater from drainages to convey it toward the surface with no use of energy. The present article highlights the socio-economic aspects of the sustainability of the QWSs and gives a satisfactory explanation of why the QWSs should be restored. In doing so, we subscribe to the view that indigenous and scientific knowledge should be incorporated. The former serves to tackle the restoration of the QWSs, the latter contributes to the distribution of water into the farmlands as efficiently as possible. Measured by (a) resilience, (b) reliability, (c) vulnerability, and (d) sustainability, the GIS technique made clear the performance of the QWSs has, therefore, the worst condition observed in terms of resiliency; the best condition observed concerning the vulnerability. Moreover, the QWSs have intermediate performance in terms of reliability. Finally, the sustainability index (SI) classifies the QWSs into different bands, which provide explicit support to take priority of the selection of the QWSs for restoration. In conclusion, a theoretical framework has been drawn to keep the QWSs sustainable.

Abstract: Study region Transboundary aquifers (TBAs) of Africa. Study focus Review of work on TBAs in Africa, including an overview of assessments and management efforts that have taken place over the last half century. New hydrological insights Seventy-two TBAs have been mapped in Africa. They underlie 40% of the continent, where 33% of the population lives, often in arid or semi-arid regions. TBA inventories have progressed since 2000 and remain work in progress. Despite their importance only eleven TBAs have been subjected to more detailed studies. Cooperation has been formalised for seven TBAs. Most of these TBAs are in North Africa and the Sahel. The recent global Transboundary Waters Assessment Programme compiled information at the national level to describe TBAs in terms of key indicators related to the water resource, socio-economic, and legal and institutional conditions. Availability of data at national level is low, hampering regional assessment. Comparing indicators, from questionnaire surveys, with those from a global water-use model showed variable levels of agreement, calling for further research. Reports on agreements scoping TBA management, indicate that this may be dealt with within international river/lake agreements, but reported inconsistencies between TBA sharing countries also indicate that implementation is limited. Increasing awareness and support to joint TBA management is noticeable amongst international organisations. However, such cooperation requires long-term commitment to produce impacts at the local level.

Abstract: Study Region: Bandung groundwater basin, Indonesia. Study focus: Groundwater abstraction of various magnitudes, pumped out from numerous depths in a multitude of layers of aquifers, stimulates different changes in hydraulic head distribution, including ones under vertical cross-sections. This generates groundwater flow in the vertical direction, where groundwater flows within its storage from the shallow to the underlying confined aquifers. In the Bandung groundwater basin, previous studies have identified such processes, but quantitative evaluations have never been conducted, with data scarcity mainly standing as one of the major challenges. In this study, we utilize the collated (1) environmental water tracer data, including major ion elements (Na+/K+, Ca2＋, Mg2+, Cl−, SO42−,HCO3−), stable isotope data (2H and δ18O), and groundwater age determination (14C), in conjunction with (2) groundwater flow modeling to quantify the aquifer interaction, driven mainly by the multi-layer groundwater abstraction in the Bandung groundwater basin, and demonstrate their correspondence. In addition, we also use the model to quantify the impact of multi-layer groundwater abstraction on the spatial distribution of the groundwater level changes. New hydrological insights for the region: In response to the limited calibration data availability, we expand the typical model calibration that makes use of the groundwater level observations, with in-situ measurement and a novel qualitative approach using the collated environmental water tracers (EWT) data for the model evaluation. The analysis in the study area using EWT data and quantitative methods of numerical groundwater flow modeling is found to collaborate with each other. Both methods show agreement in their assessment of (1) the groundwater recharge spatial distribution, (2) the regional groundwater flow direction, (3) the groundwater age estimates, and (4) the identification of aquifer interaction. On average, the downwelling to the deeper aquifer is quantified at 0.110 m/year, which stands out as a significant component compared to other groundwater fluxes in the system. We also determine the unconfined aquifer storage volume decrease, calculated from the change in the groundwater table, resulting in an average declining rate of 51 Mm3/year. This number shows that the upper aquifer storage is dwindling at a rate disproportionate to its groundwater abstraction, hugely influenced by losses to the deeper aquifer. The outflow to the deeper aquifer contributes to 60.3% of the total groundwater storage lost, despite representing only 32.3% of the total groundwater abstraction. This study shows the possibility of quantification of aquifer interaction and groundwater level change dynamics driven by multi-layer groundwater abstraction in a multi-layer hydrogeological setting, even in a data-scarce environment. Applying such methods can assist in deriving basin-scale groundwater policies and management strategies under the changing anthropogenic and climatic factors, thereby ensuring sustainable groundwater management.