Study site
The survey was carried out in Mwea, Bura, Hola, Ahero and West Kano rice schemes. Mwea Irrigation Scheme is located in Kirinyaga County and falls within two sub-counties (Mwea East and Mwea West). The scheme accounts for over 70% of the country’s rice production and covers an approximate area of 26,000 acres under paddy rice production while the remaining area is utilized for settlement, public utilities and the growing of subsistence crops. The scheme lies along the drainage basins of Rivers Nyamindi and Thiba which supply the irrigation water. River Nyamindi serves Tebere, Ndekia and Kiamanyeki sections while Thiba river serves Mwea, Thiba, Wamumu, Karaba and Kandongu sections. The area receives a mean annual rainfall and temperature of about 900- 1200 mm and 21.5 °C, respectively. Ahero and West Kano Irrigation Schemes are located in Kisumu County with a cumulative area of about 10,000 acres under irrigation. They are served by two irrigation water sources i.e. River Nyando and Lake Victoria, respectively. The area experiences a mean annual temperature and rainfall of ~ 22.9oC and ~1300 mm, respectively. Hola (Tana Delta irrigation scheme) and Bura Irrigation schemes are located in Tana River County in the Lower Tana Basin. Bura scheme has a tenant population of 2245 farmers settled in 11 villages with an irrigatable area of 12000 acres. Green grams, maize, cowpeas, cotton, watermelon, rice and onions are the primary crops cultivated. Tana Delta scheme is the oldest National Irrigation Authority scheme in the country. The scheme is about 12630 acres with 5000 acres under irrigation. The main crops cultivated here include maize, rice, cotton, watermelon, green grams, onions, pasture and other horticultural crops. Tana River County has a hot and dry climate. Average annual temperatures are about 30oC. The highest midday temperature may be above 40oC around January-March with the lowest temperature being around 20oC in June-July. Supplementary file 1 shows the survey locations including GPS coordinates.