Decline of Static Water Level in Quetta Sub-basin, Balochistan, Pakistan
Keywords:Static water level; aquifer; alluvial aquifer; recharge; Quetta; sub-basin; Balochistan Pakistan;
Background: Quetta is the most populated city of Balochistan, situated in a valley, called Quetta Sub-basin, apart of the Pishin Sub-basin, situated in northern part of the Kirthar Belt, comprising formations of Lower Jurassic through Holocene age. The Baleli River, along with its ephemeral streams, flows generally northwards, drains out of the Quetta Sub-basin near Baleli and joins the Pishin Sub-basin. It comprises two types of aquifers; 1) Alluvial aquifer, comprising horizontally-lying Quaternary alluvial succession, composed of siltstone, mudstone, sandstone and conglomerate, having primary porosity; 2) Limestone aquifer, composed mostly of Jurassic limestone, having secondary porosity. Decline of water level is detected in Sub-basin, which needs proper attention by the concerned authorities.
Objectives: The main objective was to estimate decline in the static water level in the alluvial and limestone aquifers of the Quetta Sub-basin.
Methods: Out of 430 tube wells of Quetta Water and Sanitation Authority (Q-WASA), 40 were randomly selected for monitoring for a period from April 2019 to March 2020. We selected 9 tube wells from the Limestone and 31 from the Alluvial aquifer. Decline in static water levels was estimated by taking average static water levels of both aquifers and estimating decline through formula of well-level data method. Water levels were measured by Sonic Water Level Meter and Water Level Meter Model-102 Manual.
Results: The findings show that a decline of the static water level was detected both in Limestone and Alluvial aquifers, during the period from April 2019 to March 2020, which is estimated as 0.2 m in the Limestone aquifer, and 0.99 m in the Alluvial aquifer.
Conclusions: Our results confirm that decline of the static water level dangerously continues and drastic steps are needed regarding groundwater recharge and appropriate management, in order to cope with the critical situation of water shortages in Quetta.