The drivers of water abstraction and river water diversion in tropical rivers: a case of south west upper tana basin, Kenya

Abstract

The study to determine the drivers of water abstraction and river water diversion in tropical rivers was undertaken in four rivers that constitute the South West Upper Tana Basin in Kenya. Rainfall and river discharge data for the period between years 1998 and 2018, water abstraction data and field survey data collected through questionnaires was used in this study. The water abstraction data was collected for a period of one year, from January 2018 and December 2018. The analysis of the drivers was guided by the DPSIR framework. Regression and correlation analysis was used to test the nature and strength of relationship of variables respectively. The results of the study indicate that the main drivers of water abstraction and river water diversion are climate change, government policies and strategies, agricultural development and population pressure. 60% of the people in this basin rely on agriculture hence irrigation agriculture has intensified water abstraction in the basin. There is a significant positive relationship between water abstraction and crop production with a correlation coefficient of 0.78 and coefficient of determination of 0.73. The study also established that water abstraction increased during dry season and when the rainfall received in the area decreases. The relationship between rainfall and streamflow show that increase in rainfall leads to subsequent increase in streamflow with a correlation coefficient of 0.70 and coefficient of determination of 0.61. Government policies of intensifying irrigation agriculture in order to improve food security and inter basin water transfers to improve water supply in urban and rural areas have increased water abstraction in the basin. The study recommends frequent monitoring of the rivers by authorities and licensing of all water abstractors to improve sustainability in the abstraction of water.