Case study on groundwater prospecting in Kirinyaga
An Overview of the study area
Kirinyanga district receives a bimodal rainfall pattern with two cropping seasons per year, with 60% rainfall at 350 400 mm during long rains that is reliable for good yield potential subject to availability of water. During short rains the area receives 250-300mm which is poorly distributed characterized with high risk for dry spells and droughts. This result to food insecurity with increased population, crop failures are common occurrence, rainfed cropping to subsistence levels and high evaporation rates affect crop production adversely.
To ensure food security and better livelihoods, agricultural production must be stepped up to meet the necessary demands. One way of improving crop water status is to irrigate crops fully. This is only possible when water is abstracted from rivers, lakes, storage tanks and underground aquifers. Water resources are not always where they are needed. Long distance to water sources, poor quality and low quantity of water, scarcity in terms of demand and supply and poor water management skills are some of the problems farmers face. Lack of technologies on water harvesting, conservation and groundwater prospecting are common in most rural communities.
Groundwater represents a valuable resource, whose real distribution not always related to surface rainfall patterns. Where the water table does not reach the ground to come out in form of springs, the groundwater can be reached by boring down to the porous rock, often made of sedimentary parent material or seepage line (underground stream). The water held in such reservoirs is known as aquifer. A well is formed when excavation reaches the zone of this saturated water.
Among the various sources of supply, groundwater is by far the most practical and safe in nature. It has the following advantages:
It is likely to be free of pathogenic bacteria.
Generally; it may be used without further treatment.
In many instances, it can be found in the close vicinity of the rural communities.
Almost every farming community will have access to water
The water bearing structure from which it is drawn usually provide a natural storage at the point of intake
It is relatively affordable and cost effective (especially shallow wells - up to 33 m deep).
It also has the following disadvantages:
Groundwater is often high in mineral content
It usually requires pumping
Once polluted, it could take a long time and a lot of resources to reclaim its original quality
Cluster grouping In Kirinyaga, a visionary move to have all households get access to water has been made in six locations. Seven cluster groups have been formed. PRA Participatory Rural analysis was carried out in each of the focal area where the community is mobilized to identity their problems, explore existing opportunities and come up with action plans. Common Interest Groups (CIGs) were then established for each intervention. Water prospecting was adapted in these communities that included: - shallow wells, large diameter wells and roof catchment system as enumerated in the map and the underlying text.