Thanks to the Water Act of 2016, water harvesting, storage and management is receiving attention both at the national and local levels. Following is a review of the law, practices, and design principles of water harvesting and storage in Kenya.
The Water Act of 2016 is the guiding regulation for the management and exploitation of water resources in Kenya. The Act provides for the formulation of the National Water Strategy to be the basis of use of water resources in the nation. Furthermore, the Act created key institutions involved in the management of water in the country. At the national level, these institutions include the Water Resources Authority, the National Water Harvesting and Storage Authority, the Water Sector Trust Fund, and the Water Services Regulatory Board. At the regional level, the Act created Basin Water Resources Committee and Water Works Development Agencies. At the sub basin level, the Act provides for the formation of Water Resources Users Associations and Water Service Providers under county governments. The Act also provides for catchment, ground water, and environmental conservations initiatives.
At the National Level, the National Water Harvesting and Storage Authority is the body in charge of water harvesting initiatives. At the moment, the authority focuses on four areas of water harvesting namely large dams, small dams and water pans, boreholes, and flood control. At the household level, water harvesting remains largely unregulated. As a result, most of home based water harvesting interventions are not very effective. For sound water harvesting, proper planning and design is required. One also needs sound grounding on the various theoretical concepts of water harvesting and storage.
3. Classes of water harvesting in Kenya
Water harvesting in Kenya is broadly classified into flood water, macro catchment, micro catchment and roof top harvesting. Flood water harvesting entails harvesting water from outside the affected site to prevent it from eroding the land, while harvesting it for other uses. Some of the interventions here include diversion of spate flow and flood water interception. Macro catchment harvesting entails harvesting water from outside a farm, while micro catchment entails trapping localized runoff mostly at the farm level. Roof top harvesting, which is the most common, entails harvesting rainfall through roof tops and accompanying structures.
4. Design of Water Harvesting Structures
For best results, water harvesting structures have to be designed. Here, due regard must be given to the soils, rainfall, and catchment characteristics. On soils, the texture, structure, infiltration, depth, salinity, and water holding capacity are some of the important design factors to use when assessing the viability of constructing a water harvesting structure, especially subsurface structures, which rely on the soil for stability. Important rainfall data during design includes rainfall intensity, duration, amount and distribution. Vital catchment information in design includes the surface cover, slope and runoff coefficients to uses in calculations.