Determination of crop water requirements in relation to available and domestic water supply demands in Nguruman Irrigation Scheme, Kajiado County, Kenya
Lack of organized production systems, optimum cropping patterns and crop water requirements has lead to blanket application of irrigation water, causing low irrigation efficiency in Nguruman Irrigation Scheme. Therefore, the objective of the research was to determine appropriate cropping systems and crop water supply requirements in relation to available water from the source and domestic needs. The crops provided by the Divisional Agricultural Extension Officer were selected, being assumed to be the farmers’ choices, in which food security was given the highest priority, followed by vegetables and fruit trees, covering 52.5, 29.6 and 17.9% of the total project area respectively. The crop water requirements were determined, using the conventional methods. The selected crops were planned to be grown in three phases. Phase one comprised beans (40 ha), onions (40 ha), pasture (40 ha), banana (40 ha) and maize (65 ha). Phase two consisted of: soybean (65 ha), ravaya (80 ha), pasture (40 ha), mangoes (30 ha) and sorghum (35 ha). Phase three comprised of: green grams (30 ha); okra (20 ha); karella (80 ha), lemon (40 ha) and sweet potatoes (35 ha).The peak water supply requirement was found to be 332,568 m3, occurring in the month of November under maize and onions with a total acreage of 105 ha. This translated into annual water demand (water duty) of 1,766,493 m3 for irrigating 265 ha proposed for phase one. For the proposed project area of 800 ha, the total water supply requirement was found to be 5,333,809 m3/year, while the domestic water supply requirement for human and livestock consumption was found to be 74,664 m3/year, culminating into a total scheme water supply demand of 5,408,493 m3/year. The current water supply from the source, being 28,382,400 m3/year, is enough to meet irrigation and domestic water needs. However, there is bound to be a significant increase in irrigation and domestic water needs in the near future if all the irrigable land of 3,000 ha is brought under production by more farmers migrating from other regions into the scheme with increased number of livestock. The most immediate irrigation practice recommended to counter this scenario is to stagger the crops so that crops with high water demands do not concur with their peaks in the period with the highest evaporative demands. For long term perspective, water saving techniques and irrigation methods with high efficiency are recommended to ensure that the production objectives are sustained.
Key words: Crops, crop water requirements and water supply demands
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