Flood Storage and River Water Abstraction

The upper Ewaso Ng&s;iro basin, which starts from the central highlands of Kenya and stretch northwards transcending different climatic zones, has experienced decreasing river flows for the last two decades. The Naro Moru sub-basin is used to demonstrate the looming water crisis in this water scarce river basin. The decreasing flows are attributed to over-abstraction mainly for irrigating horticultural crops. The number of abstractors has increased 4 times over a period of 10 years. The quantity abstracted has also increased by 64% over the last 5 years. Ironically, the proportion of unauthorized abstractions has been increasing over the years, currently at about 80% and 95% during high and low flows respectively. This has resulted in alarming conflicts among various water users. The situation is aggravated by low irrigation efficiency (25-40%) and lack of flood flow storage facilities. The chapter analyzes over 40 years’ observed river flow data and 5-year interval water abstraction monitoring records for 15 years.