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International Institute for Aerospace Survey, Netherlands (2000)

The long term interaction of groundwater with Lake Naivasha, Kenya. A numerical simulation of the relationship between groundwater and lake allowing for fluctuating lake levels

Owor, Micheal

Titre : The long term interaction of groundwater with Lake Naivasha, Kenya. A numerical simulation of the relationship between groundwater and lake allowing for fluctuating lake levels

Auteur : Owor, Micheal

Etablissement de soutenance : International Institute for Aerospace Survey, Netherlands

Grade : Master of Science (MSc) 2000

Résumé
The long-term interaction of groundwater with Lake Naivasha allowing for fluctuating lake levels over 66 years (1932-1997), was numerically simulated under steady state and transient conditions. A Lake Package that simulates lake-groundwater interaction with MODFLOW was used. The results show that the accuracy of the digital terrain model is important to consider so as to safeguard the integrity of the ensuring hydrologic model and its applications. Automatic calibration of a model of this complexity is fast, efficient and quantifies the degree of uncertainty in the model results. The similarity in the budget components of the steady state and transient runs indicate that the hydrologic system had nearly reached a state of dynamic steady state equilibrium prior to the onset of the present level of water abstraction. There is a temporal variation in groundwater seepage from the lake that responds to the peak hydrologic inflow events to the lake. The rise in lake levels are associated with only those periods when stream/runoff inflows to the lake are in excess of the outflows. Consistent net groundwater outflow from the lake that averages 4.76 million cubic meters per month is evident. The regional groundwater flow patterns indicates major outflow areas to the south and south-east of the basin and lesser to the north and north-east. Temporal and spatial variations in the nature and magnitudes of groundwater-lake interactions, vertical flow and storage, abound around the lake. The extent of the zone of influence of the lake varies with the direction. The northern and western parts of the lake show the highest fluctuations in lake-groundwater flow interactions. The response of the groundwater levels to selected periods of lake level rise, fall and stability shows mimicry. There is a significant amount of water abstraction that has been picking up since 1980. The results are instrumental in providing a more realistic insight into the long-term interaction of the lake and groundwater for this kind of system affected by transience.

Sujets : Lake Naivasha, Kenya ; Groundwater ; Hydrology ; Watershed ;

Présentation

Page publiée le 29 décembre 2016, mise à jour le 18 octobre 2018