URBANIZATION EFFECTS on WATER RESOURCES IN QUETTA VALLEY PAKISTAN

Extensive groundwater withdrawals in urban areas may cause water shortages, land subsidence and water quality problems. Quetta Valley is the largest population center of Balochistan province in western Pakistan. This area is arid and groundwater is the main source for domestic and agricultural use. There is generally paucity of hydrogeologic studies in this region, currently an integrated interdisciplinary groundwater exploration studies are underway that include construction and calibration of rainfall-runoff models and water quality studies. Our work suggests that Quetta Valley has experienced progressively increasing decline in groundwater levels in the last three decades. Water and Sanitation Authority of Quetta (WASA) is monitoring groundwater levels since 1989 and in some parts of the valley water decline up to 24 meters in 30 years is reported. This work presents preliminary report on this challenge. We have assessed spatial and temporal variations of water levels. Thirty six satellite images (Landsat ETM+, TM and MSS) from 1975 to 2009 are classified and processed to quantify land cover and land use changes. Normalized Difference Vegetation Index (NDVI) data highlight increased agricultural areas in the central valley of Quetta and reduced vegetation on mountains that corresponds with gradual temporal changes in water volumes in streams and lakes. In addition, average temperatures increased and mean precipitation decreased during this time period. However, the biggest change in this area is in population growth which rose from 260,000 in 1975 to 1.2 million in 2010 mainly because of migration of refugees from war-torn neighboring Afghanistan. The decline in water level has serious consequences in this region; for example recent studies indicate subsidence in the valley. Drinking groundwater samples from Quetta Valley also demonstrate high concentrations of nitrate, sulfate, arsenic, selenium, chromium and nickel. Considering all these issues with groundwater, WASA are investigating alternate groundwater resources and drilled several exploratory wells some of those are successful and are tapping water from the limestone aquifer. Quetta valley provides a good example to study the impact of urbanization on water resources.