Irrigation performance indicators
Irrigation performance indicators
Irrigation performance indicators are crucial in monitoring the spatial and temporal performances of the scheme, and looking for causes and providing advice to improve the overall productivity of the scheme. Some of the key indicators include adequacy and beneficial fraction or efficiency.
- Adequacy
Adequacy is estimated as the ratio of seasonal actual evapotranspiration (ETa) to seasonal potential evapotranspiration (ETp). It is therefore a measure of the degree of agreement between the actual water use and crop water requirement. As shown in Figure 1 below, the adequacy levels for the Mwea irrigation scheme in the year 2021 were significantly low compared to 2019. This is indicative of the impacts of drought experienced across the Kenya in 2019.

Figure 1: Irrigation adequacy in the Mwea Irrigation scheme in 2019 and 2021
- Beneficial Fraction
Beneficial fraction is estimated as the ratio of the water that is consumed as transpiration to overall field water consumption (ETa). It therefore shows the efficiency of on farm water and agronomic practices in use of water for crop growth. Figure 2 below shows the beneficial fraction for the Mwea Irrigation scheme for year 2019 and 2021. Similar to the adequacy levels, the irrigation efficiency in 2021 was low due to inadequate supply of water across the scheme.
Figure 2: Irrigation beneficial fraction/efficiency in the Mwea Irrigation scheme in 2019 and 2021