In the near future climate change is expected to increase the severity of droughts in semi-arid regions. Moreover, rainy seasons are expected to become shorter and more intense. Subsequently, water stress will increase, as inhabitants are dependent on rain-fed agriculture. Recent examples of increased water stress are the droughts in the Horn of Africa. Water harvesting is showing a potential adaptation measure to cope with the expected increase in water stress. In Kitui, Kenya water harvesting systems like sand dams, cisterns and open ponds are used to harvest water. Little is known about the influence of evaporation on these water harvesting systems. In this research, sixteen methods of evaporation are compared with the residual of the energy balance and six methods are analyzed for their influence of modeled water harvesting systems (i.e. open pond and sand dam). The Priesley-Taylor method shows the best results (r2 of 0.99, Nash-Sutcliffe efficiency of 0.78). Other methods showing agreeable results are Granger-Gray, Morton’s CRAE, Brutsaert-Strickler, Penman-Monteith and Bowen Ratio Energy Balance. Six analyzed evaporation methods for modeled water storage show a deviation ranging between -24 to 10 % and -27 to 8 % of evaporative fracture for open pond and sand dam respectively. The deviation of evaporative fracture equals up to 3.5 and 2.5 % of total water harvested, in open pond and sand dam respectively, for the analyzed period. The influence of the evaporation and selected evaporation methods seem less important than other fluxes when looking into water harvesting systems.
The MSc report can be accessed here: MSc_Evaporation and water storage in semi-arid region of Kitui, Kenya
Last modified: September 11, 2017