Assessing the Relationship between the Growth of Population and Crop Area with Depletion of Groundwater in Lower Bari Doab Canal

摘要

An increase in crop water requirement due to surge in population has urged the integration of groundwater with a canal for irrigation in Pakistan. As the cropping intensity grew from 102.8% in 1960 to 172% in early 2010 in certain areas, replenishment of groundwater has been challenged. This caused Lower Bari Doab Canal (LBDC) in Punjab to experience groundwater depletion in the last two decades. Literature reports the rate of depletion that ranges from 0.259 to 0.594 cm per year beyond 1990 in the observation wells in the canal division. This study proposes to analyze the correlation between population growth, crop coverage, and water table depletion rate in the districts irrigated by LBDC: Okara, Sahiwal, and Khanewal. It uses publicly available yearly statistical data published by the Bureau of Statistics, Pakistan. The data sets include population count and area irrigated under four dominant crops (wheat, rice, cotton, and sugarcane), precipitation, and temperature. The study period ranges from 1990 to 2010. There is an evergrowing population in all three districts. A non-parametric Mann-Kendall test revealed an increasing trend in the cultivation of total major crops in the command area. A simple correlation test is performed to relate various climatic, anthropogenic, and agricultural factors with varying depletion rates of groundwater in the districts. Overlaying the observation well locations over districts in GIS, three of them were allocated to Khanewal, two to Okara, and one to Sahiwal. The results show that the spatially variable depletion rates can be explained by the growth of population, cropped area, rainfall, temperature, and evapotranspiration. This emphasizes the need for flexible policies especially targeting the tail reach of the command area. Our study has also pointed out the most severe condition of groundwater lies in Khanewal. Therefore, restriction in the abstraction of water, artificial recharge, and other demand management techniques should be practiced in the region. The results of this study hope to bring awareness regarding the importance of conserving groundwater sources.