Ammonium and nitrate contamination source and dynamics in groundwater of Kathmandu Valley, Nepal
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Groundwater Contamination
Ammonium nitrate
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Repeat sampling and age tracers were used to examine trends in nitrate, arsenic, and uranium concentrations in groundwater beneath irrigated cropland. Much higher nitrate concentrations in shallow modern groundwater were observed at both the Columbia Plateau and High Plains sites (median values of 10.2 and 15.4 mg/L as N, respectively) than in groundwater that recharged prior to the onset of intensive irrigation (median values of <1 and <4 mg/L as N, respectively). Repeat sampling of these well networks indicates that high nitrate concentrations in modern, shallow groundwater have been sustained for decades, posing a future risk to older, deeper groundwater used for drinking water. In fact, nitrate concentrations in older modern water (30–60 years since recharge) at the High Plains site have increased in the past decade. Groundwater irrigated areas in the Columbia Plateau tend to have higher nitrate concentrations in groundwater than surface water irrigated areas, suggesting repeated dissolution of land applied fertilizer during recirculation may be an important factor causing high nitrate concentrations in groundwater. Mobilization of uranium and arsenic by land surface activities is suggested by the higher concentrations of these constituents in modern, shallow groundwater than in older, deeper groundwater at the Columbia Plateau site. Bicarbonate concentrations in modern groundwater are positively correlated with uranium (r = 0.72, p < 0.01), suggesting bicarbonate may mobilize uranium in this system. A positive correlation between arsenic and phosphorus concentrations in modern groundwater (r = 0.55, p < 0.01) suggests that phosphate from fertilizer outcompetes arsenate for sorption sites, mobilizing sorbed arsenic derived from past pesticide use or other sources.
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Anhydrite
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This article briefly deals with the nature of the aquifers and total groundwater reserves of the Kathmandu Valley. It is attempted ·to evaluate and estimate the total groundwater resources in the Valley. Based on the present condition it is suggested to prevent over exploitation situation of groundwater resource and to increase the perennial yield through artificial methods of groundwater recharge.
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The contamination of groundwater by geogenic arsenic is the cause of major health problems in south and southeast Asia. Various hypotheses proposing that As is mobilized by the reduction of iron (oxy)hydroxides are now under discussion. One important and controversial question concerns the possibility that As contamination might be related to the extraction of groundwater for irrigation purposes. If As were mobilized by the inflow of re-infiltrating irrigation water rich in labile organic carbon, As-contaminated groundwater would have been recharged after the introduction of groundwater irrigation 20-40 years ago. We used environmental tracer data and conceptual groundwater flow and transport modeling to study the effects of groundwater pumping and to assess the role of reinfiltrated irrigation water in the mobilization of As. Both the tracer data and the model results suggest that pumping induces convergent groundwater flow to the depth of extraction and causes shallow, young groundwater to mix with deep, old groundwater. The As concentrations are greatest at a depth of 30 m where these two groundwater bodies come into contact and mix. There, within the mixing zone, groundwater age significantly exceeds 30 years, indicating that recharge of most of the contaminated water occurred before groundwater irrigation became established in Bangladesh. Hence, at least at our study site, the results call into question the validity of the hypothesis that re-infiltrated irrigation water is the direct cause of As mobilization; however, the tracer data suggest that, at our site, hydraulic changes due to groundwater extraction for irrigation might be related to the mobilization of As.
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Research Article| February 21 2014 Water resources and the potential of brackish groundwater extraction in Egypt: a review A. Nashed; A. Nashed 1School of Photovoltaic and Renewable Energy Engineering University of New South Wales, Sydney, NSW, Australia E-mail: a.sproul@unsw.edu.au Search for other works by this author on: This Site PubMed Google Scholar A. B. Sproul; A. B. Sproul 1School of Photovoltaic and Renewable Energy Engineering University of New South Wales, Sydney, NSW, Australia Search for other works by this author on: This Site PubMed Google Scholar G. Leslie G. Leslie 2School of Chemical Engineering, University of New South Wales, Sydney, NSW, Australia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2014) 63 (6): 399–428. https://doi.org/10.2166/aqua.2014.162 Article history Received: September 18 2013 Accepted: December 18 2013 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation A. Nashed, A. B. Sproul, G. Leslie; Water resources and the potential of brackish groundwater extraction in Egypt: a review. Journal of Water Supply: Research and Technology-Aqua 1 September 2014; 63 (6): 399–428. doi: https://doi.org/10.2166/aqua.2014.162 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex A review of water resources in Egypt indicates that Nile water is fully utilized and the available quantity could potentially decrease by approximately 19% due to proposed water usage by neighboring countries. Seawater desalination and groundwater extraction are the only options to increase Egypt's water supply. The extraction and desalination of brackish groundwater is suggested to develop sustainable decentralized communities. A review of seven main hydro-geological systems across six regions in Egypt is conducted to identify areas with access to brackish groundwater and aquifers are ranked on the potential for sustainable development using multi-criteria analysis based on literature data for productivity, renewability, groundwater depth and development potential. Approximately 55% of Egypt's area has access to brackish groundwater, 47% of which has access to aquifers with moderate to high potential for development. Five high priority areas have been identified for establishing decentralized communities based on brackish groundwater extraction: Areas with access to the Nubian aquifer, the Quaternary aquifer in the central parts of the Sinai Peninsula, in the vicinity of the Nile River in the Eastern Desert and the Western Desert south of Cairo, and the coastal aquifers along the north west Mediterranean coast and the Suez Gulf. brackish groundwater, decentralization, desalination, Egypt, solar energy, sustainable development This content is only available as a PDF. © IWA Publishing 2014 You do not currently have access to this content.
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Groundwater is no longer an open-access resource in Kathmandu. Perceptions of groundwater are changing from an “infinite” to a “finite” resource and the role of the government from supply developer to caretaker of the resource. In this context, this paper aims to unfold how perceptions of groundwater in Kathmandu Valley, Nepal, are changing from an open-access resource to an overexploited, depleted, degraded, vulnerable and state-controlled resource. In the process, it produces an aggregated picture of resource availability, development dynamics, impacts and responses in the area; suggests some “soft-path” approaches for groundwater management; and discusses implications of the experience for other areas.
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