Cropping Choices and Farmers’ Options

Irrigation being the main cause of aquifer depletion, agriculture is the first candidate to contribute to its solution. Options of agricultural planting structure in Beijing-Tianjin-Hebei region are analyzed using various planting scenarios.

Way Forward

The combination of fallowing and substituting groundwater by surface water was effective in reducing aquifer depletion in Guantao. The average annual depletion rate after 2014 was about half the value of the pre-project period 2000–2013 and basically limited to the deep aquifer. The goal of closing all deep aquifer wells has only been reached partially, their use being necessary in locations where the shallow aquifer is too saline.

Mining sector methods will evolve to meet climate aims

Significance Miners have started to introduce innovative technologies to improve sustainability and most are targeting emissions reductions. However, approaches and ambitions differ, and the EU is yet to extend its sustainability measurements to mining. Impacts Anglo American has announced plans to divest from coal assets; any other miners with coal assets are likely to follow. Russia’s gold miner Polymetal has a six-year ‘green loan’ to invest in projects that will cut the environmental impact of its operations. Faced with water stress in Chile, lithium producer SQM is devising new ways to reduce its operations’ impact on aquifer depletion.

Characterizing Riverbed Heterogeneity across Shifts in River Discharge through Temporal Changes in Electrical Resistivity

The fluxes between groundwater and surface water play a significant role in quantifying water balance along stream reaches to continent scales. Changes in these dynamics are occurring due to aquifer depletion, where pre-development baseflow conditions have transitioned to losing conditions. This problem is studied along the Arkansas River in Western Kansas across a stream reach that transitions from near steady state to losing conditions, and contributes focused recharge to a depleting Ogallala Aquifer. Existing hydrologic data illustrates the lack of understanding they provide related to the control of fluxes exerted by alluvial deposits. Electrical resistivity imaging (ERI) surveys were conducted along this river transect to elucidate the dynamic hydrologic connection existing between the Arkansas River and underlying Arkansas Alluvial and Ogallala Aquifers. Temporal changes in ERI profiles are associated with the transient hydrologic conditions below the water-sediment interface, and complement the hydrogeologic interpretations of the individual ERI profiles. Additionally, fine grained soil inclusions may become revealed by temporal changes in resistivity due to differences in their water holding capacity relative to that of a surrounding matrix of coarser grained soil across changes in recharge. These findings corroborate the role of river-aquifer connectivity and riverbed heterogeneity on localized recharge through embedded assemblages of fine and coarse grained soils.

Lessons to Be Learned: Groundwater Depletion in Chile’s Ligua and Petorca Watersheds through an Interdisciplinary Approach

Groundwater (GW) is the primary source of unfrozen freshwater on the planet and in many semi-arid areas, it is the only source of water available during low-water periods. In north-central Chile, there has been GW depletion as a result of semi-arid conditions and high water demand, which has unleashed major social conflicts, some due to drought and others due to agribusiness practices against the backdrop of a private water management model. The Ligua and Petorca watersheds in the Valparaíso Region were studied in order to analyze the influence of climatic and anthropogenic factors on aquifer depletion using an interdisciplinary approach that integrates hydroclimatic variables, remote sensing data techniques, and GW rights data to promote sustainable GW management. The Standardized Precipitation Index (SPI) and Normalized Difference Vegetation Index (NDVI) were calculated and the 2002–2017 land-use change was analyzed. It was shown that GW decreased significantly (in 75% of the wells) and that the hydrological drought was moderate and prolonged (longest drought in the last 36 years). The avocado-growing area in Ligua increased significantly—by 2623 ha—with respect to other agricultural areas (higher GW decrease), while in Petorca, it decreased by 128 ha. In addition, GW-rainfall correlations were low and GW rights were granted continuously despite the drought. The results confirmed that aquifer depletion was mostly influenced by human factors due to overexploitation by agriculture and a lack of water management.

Evaluating the Impacts of Pumping on Aquifer Depletion in Arid Regions Using MODFLOW, ANFIS and ANN

In arid regions, the groundwater drawdown consistently increases, and even for a constant pumping rate, long-term predictions remain a challenge. The present research applies the modular three-dimensional finite-difference groundwater flow (MODFLOW) model to a unique aquifer facing challenges of undefined boundary conditions. Artificial neural networks (ANN) and adaptive neuro fuzzy inference systems (ANFIS) have also been investigated for predicting groundwater levels in the aquifer. A framework is developed for evaluating the impact of various scenarios of groundwater pumping on aquifer depletion. A new code in MATLAB was written for predictions of aquifer depletion using ANN/ANFIS. The geotechnical, meteorological, and hydrological data, including discharge and groundwater levels from 1980 to 2018 for wells in Qassim, were collected from the ministry concerned. The Nash–Sutcliffe efficiency and mean square error examined the performance of the models. The study found that the existing pumping rates can result in an alarming drawdown of 105 m in the next 50 years. Appropriate water conservation strategies for maintaining the existing pumping rate can reduce the impact on aquifer depletion by 33%.

Groundwater depletion in the upper aquifer of the chad formation, Chad basin, North-Eastern Nigeria

This paper examines the present groundwater level changes in the Upper aquifer of Chad Formation in Borno basin measured in the year 2007, 2008, 2009, 2011 and 2012. The study involved collection of topographic maps of scale 1:500,000 on Nigerian sheet 4 covering the study area. Previous published literatures on the basin were also collected. Hand dug wells and their elevation were located and measured with satellite navigator. Findings from the results shows that, the Upper aquifer is a phreatic aquifer separated by thin clay layer into “A” sub-zone with depth ranging from 1 to 10 m, “B” sub-zone with depth ranging from 10 to 60 m and “C” sub-zone with depth ranging from 60 to 100 m. From the study, it can be deduced that, the C sub-zone is not recharging from seasonal infiltration of meteoric water or from the horizontal stream flow, it rather shows a depleting groundwater level. It was proved that rain of wet seasons do not recharge Upper C sub-zone to the previous wet season level, and thus the water table in the Upper C zones will be exhausted if the aquifer is not recharged at the present level of abstraction. Keywords: Groundwater, Chad Basin, Phreatic aquifer, Depletion level and Upper aquifer.