Modelling the Influence of Groundwater Abstractions on the Water Level of Lake Naivasha, Kenya Under Data-Scarce Conditions

Abstract

This study presents the state-of-the-art understanding of the data-scarce and hydrogeologically complex groundwater system of Lake Naivasha, Kenya, with the particular aim of exploring the influence groundwater abstractions have on Lake Naivasha's water level. We developed multiple alternative but plausible parameterizations for a MODFLOW groundwater model, based on literature, existing models and available data, while trying not to overcomplicate the model. In doing so, we illustrate a possible strategy of going about data-scarce regions in modelling in general. Processes encountered in the calibrated parameterizations show groundwater flows laterally from the escarpments to the valley floor and axially from the lake along the Rift, with a larger portion flowing out southward than northward. Extraction of groundwater interrupts the flow from the northwestern highlands to the lake, leading to a lake stage reduction of 0.7-7.5 cm due to abstractions at our target farm (Flower Business Park) or an implied 7-75 cm due to total groundwater abstractions in the area. Although this study demonstrates our understanding of Naivasha's groundwater system remains fragile and the current model cannot be embedded in operational water management yet, it (i) reflects the contemporary understanding of the local groundwater system, (ii) illustrates how to go about modelling in data-scarce environments and (iii) provides a means to assess focal areas for future data collection and model improvements.

Capping Human Water Footprints in the World's River Basins

“…For example, adopting a WF cap requires of local (water) authorities that they know—preferably in quantitative terms—local runoff, local environmental water needs, and local water consumption (e.g., through accounting WF permits that are issued to any of the various users at any given time). In ill‐managed or data‐scarce basins, accounting of incoming and outgoing flows will pose a substantial challenge, as does their monitoring (Hogeboom et al, ). With respect to institutional hurdles, attempts to incorporate what might be considered a local WF cap in South Africa were stranded in power struggles between various levels of authority (Bourblanc & Blanchon, ).…”

Interactions of artificial lakes with groundwater applying an integrated MODFLOW solution

“…The large sensitivity of lakebed seepage to λ and K, emphasizes the importance of their reliable parameterization. The importance of the λ parameter has already been Table 2 The sensitivity of lakebed seepage to changes of lakebed leakance (λ) and shallow aquifer hydraulic conductivity K when testing: (1) 4-years average of daily net lake seepage (L LKnet ); (2) daily average of lake seepage into groundwater at the maximum lake stage (L LKout ); and (3) max shoreline seepage at maximum lake stage (L LKout ); all using 10 and 0.1 multiplication factors of λ and K emphasized, for example by Hogeboom et al (2015), but large L LKnet sensitivity to the increase of shallow aquifer K, three times larger than to the increase of λ, is surprising and relevant. Fortunately, in this TL study, the λ and K were well defined; considering λ, the lakebed thickness was directly measured through regular underwater sampling schema ( Fig.…”

Water Resource Assessment of a Complex Volcanic System Under Semi-Arid Climate Using Numerical Modeling: The Borena Basin in Southern Ethiopia

“…This data issue constitutes the main limitation to groundwater models applications, specifically in developing countries, where data are often scarce and sometimes affected by high uncertainty. Some attempts have been made to overcome this issue in order to use numerical modeling in such cases [41][42][43][44].…”