Evaluation of groundwater environment of Kathmandu Valley

Abstract

Kathmandu Valley aquifer in central Nepal is continuously under stress since the commencement of mechanized extraction of groundwater resources in early 1970s. Many wells have been drilled in shallow and deep aquifers of the valley; and numerous studies have been made in last four decades to understand the aquifers. However, up-to-date information on well inventory, water extraction, water quality and overall situation of groundwater environment are not yet known in the absence of institutional responsibility in groundwater management. This study attempts to evaluate current state of the groundwater environment considering natural and social system together; to better understand origin of stresses, their state, expected impact and responses made/needed to restore healthy groundwater environment. The analysis reveals increasing population density (3,150-4,680 persons/km 2 ), urbanization (increase in urban population from 0.61 to 1.29 million) and increasing number of hotels due to tourism (23-62 hotels) during a decade are acting as driving forces to exceed groundwater extraction over recharge (extraction = 21.56 and recharge = 9.6 millioncubic meter-a-year), decrease in groundwater levels (13-33 m during 1980-2000 and 1.38-7.5 m during 2000-2008), decline in well yield (4.97-36.17 l/s during mid1980s to 1998) and deterioration in water quality. In the absence of immediate management intervention with institutional responsibility for groundwater development, regulation and knowledgebase management (i.e. to facilitate collection, integration and dissemination of knowledge); situation of groundwater environment are expected to deteriorate further. Groundwater modeling approach may help to suggest appropriate management intervention under current and expected future conditions.

The contested common pool resource: Ground water use in urban Kathmandu, Nepal

“…Inequitable distribution of water across ward number 28 is also evident which has forced over extraction of ground water. It is found that anthropogenic factors such as over-exploitation of ground water are major drivers that exert pressures on groundwater environment which has lowered the groundwater levels and raised concerns on risks of land subsidence in area with high compressible clay and silt layers (Pandey et al, 2010).…”

A GIS-based methodology to delineate potential areas for groundwater development: a case study from Kathmandu Valley, Nepal

“…The mineral composition of the aquifer material is dominated by quartz, K-feldspar, plagioclase, and mica with minor chlorite and calcite (Paudel et al 2004). The groundwater basin is home to 1.53 million people (population density is 4,690 person/km 2 ), 84.3 % of them live in urban areas (Pandey et al 2010). Groundwater is a major source of domestic water supply for those populations.…”

“…Groundwater extraction has been continuously increasing since the 1970s, with extraction exceeding recharge since the mid-1980s. This is mainly due to increase in population density from 3,150 to 4,690 persons/ km 2 during 1991-2001 (Pandey et al 2010). With no regulations on groundwater use and no management interventions, current status of achievements in sustainable groundwater management is relatively 'poor' .…”

“…However, analysis for cost and benefit should be carried out separately before deciding to launch such recharge projects. If we continue using Kathmandu Valley's groundwater reserve at the same rate as in 2001, i.e., 21.56 MCM/year (as discussed in Pandey et al 2010), shallow and deep aquifers in the valley will be emptied in less than 100 years (without considering recharge). The analysis based on estimated storage volume and rate of extraction is consistent with that of Cresswell et al (2001) based on recharge and extraction rates.…”

“…Depletion of water levels in aquifers and decline in design yield of wells due to excessive pumping in the absence of adequate knowledge on groundwater availability are becoming a major concern across the globe (Babikar et al 2005;Kendy et al 2003;Konikow and Kendy 2005;Pandey et al 2010;Reddy 2005;Saha et al 2007;Shah et al 2000). As a response to the problems, approaches like artificial aquifer recharge, managed aquifer recharge, recharge area protection, and construction of underground storage dams are being discussed and practiced to some extent (e.g., Bouwer 2002;Dillon 2005;Kumar et al 2008;Mills 2002;Scanlon et al 2002;Shah et al 2000;Tuinhof and Heederik 2003).…”