Lessons from sociohydrological phenomena in the Lake Naivasha basin, Kenya

Abstract

<p>The Lake Naivasha basin (Kenya) simultaneously supports a wetland of international importance for biodiversity conservation and agricultural activities of national economic relevance. Water demands have increased substantially over time, while land-use changes have also affected the water balance and put the ecosystem under pressure. Consequently, a wicked-problem situation has developed, with conflicting interests between stakeholders. The human influence on the water balance of Lake Naivasha and its downstream lake has increased over time which has particularly become evident during periods of drought. Several known sociohydrological phenomena have emerged in the Lake Naivasha basin. We have identified and discuss four sociohydrological phenomena: the Supply-demand Cycle, the Rebound effect, the Sequence effect, and the Reservoir effect.</p><p>The Supply-demand cycle relates to the exploitation of Lake Naivasha and its connected aquifer using pumps. With investments in groundwater pumping it has become possible to supply an increasing water demand, largely serving the flower industry (with logistics and transport). This triggered more investment, labour migration, and thus more water demand. With increasing demands and strong variations in water availability, the risk of economic loss has increased, as became clear during a recent period of drought.</p><p>The Rebound effect is seen in the context of investments in technologies for increasing irrigation efficiency. By installing drip technology and hydroponics farmers have become able to produce more with the same amount of water withdrawn. The result is an increase in total evaporation and a reduction of return flow into the lake and its connected aquifer. The resulting increased water consumption thereby offsets the water saving potential of the improved technologies. Investments are not limited to the direct surroundings of Lake Naivasha but also take place in upstream parts of the Lake Naivasha basin.</p><p>The Sequence effect has been observed when during a relatively long period with low water availability a situation had developed in which water users moved their activities closer to Lake Naivasha. This allowed them to make better use of the fertile lands and have access to the scarce water. Placing investments at lower elevations also increased their vulnerability to flood.</p><p>The Reservoir effect has been observed in relation to the growing flower industry which largely relies on lake water reserves and it’s connected aquifer. Following drought, economic losses occurred due to limited water abstraction for production of flowers. The overreliance on water infrastructures escalated society’s vulnerability and led to considerable economic losses during  a period.</p><p>This study involved integrated assessment which has yielded relevant insights into the effects of human activities on the hydrology of the area resulting in more pronounced hydrological extremes and related ecological and societal impacts. This knowledge base is useful to inform the sustainable management of the Lake Naivasha basin.</p>