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.