Groundwater Pumping For Irrigation Research Articles

Near-surface wetland sediments as a source of arsenic release to ground water in Asia

Tens of millions of people in south and southeast Asia routinely consume ground water that has unsafe arsenic levels. Arsenic is naturally derived from eroded Himalayan sediments, and is believed to enter solution following reductive release from solid phases under anaerobic conditions. However, the processes governing aqueous concentrations and locations of arsenic release to pore water remain unresolved, limiting our ability to predict arsenic concentrations spatially (between wells) and temporally (future concentrations) and to assess the impact of human activities on the arsenic problem. This uncertainty is partly attributed to a poor understanding of groundwater flow paths altered by extensive irrigation pumping in the Ganges-Brahmaputra delta, where most research has focused. Here, using hydrologic and (bio)geochemical measurements, we show that on the minimally disturbed Mekong delta of Cambodia, arsenic is released from near-surface, river-derived sediments and transported, on a centennial timescale, through the underlying aquifer back to the river. Owing to similarities in geologic deposition, aquifer source rock and regional hydrologic gradients, our results represent a model for understanding pre-disturbance conditions for other major deltas in Asia. Furthermore, the observation of strong hydrologic influence on arsenic behaviour indicates that release and transport of arsenic are sensitive to continuing and impending anthropogenic disturbances. In particular, groundwater pumping for irrigation, changes in agricultural practices, sediment excavation, levee construction and upstream dam installations will alter the hydraulic regime and/or arsenic source material and, by extension, influence groundwater arsenic concentrations and the future of this health problem.

Groundwater quality in CR-V irrigation district (Bardenas I, Spain): Alternative scenarios to reduce off-site salt and nitrate contamination

Irrigated agriculture may negatively affect groundwater quality and increase off-site salt and nitrate contamination. Management alternatives aimed at reducing these potential problems were analysed in the 15498 ha CR-V Irrigation District (Spain) by monitoring 49 wells and modelling the hydrological regime in a representative well of the Miralbueno Aquifer. Groundwaters presented low to moderate electrical conductivity (EC) (mean = 0.89 dS/m) and high [NO 3 −] (mean = 94 mg/L). The groundwater depth (GWD) during the 2001 hydrological year responded to the annual cycles of precipitation and irrigation as well as to the secondary cycles derived from irrigation scheduling. GWD were consistently simulated by the groundwater BAS-A model. Model results indicate that an increase in irrigation efficiency and the pumping of groundwater for irrigation will decrease GWD and aquifer's discharge by 56–70%, depending on scenarios. These recommendations will save good-quality water in the reservoir, will be beneficially economical to farmers, and will minimize off-site salt and nitrogen contamination.

Groundwater overdraft reduction through agricultural energy policy: insights from India and Mexico

Rapid expansion of groundwater irrigation has transformed the rural economy in regions around the world, leading to significant increases in agricultural productivity and rising incomes. Farmer investment in wells and pumps has driven this expansion on the demand side; however, the supply of cheap agricultural energy—usually electrical power—is a critical though often overlooked driver of the groundwater boom. One serious outcome in numerous regions around the world has been groundwater overdraft; where pumping exceeds aquifer recharge, water tables have declined and water quality has deteriorated. India and Mexico are two of the largest users of groundwater in the world and both face critical overdraft challenges. The two countries are compared, given that electrical energy supply and pricing are primary driving forces behind groundwater pumping for irrigation in India and Mexico alike. Both countries have attempted regulatory measures to reduce groundwater overdraft. However, with low energy costs and readily available connections, there are few financial disincentives for farmers to limit pumping. The linkages between energy and irrigation are reviewed, comparing and contrasting India and Mexico. Examples of legal, regulatory and participatory approaches to groundwater management are assessed. Finally, the implications of linking electrical power pricing and supply with ongoing groundwater regulation efforts in both countries are explored.