Modelling the water balance of Lake Victoria (East Africa) – Part 1: Observational analysis

Abstract

Abstract. Lake Victoria is the largest lake in Africa and one of the two major sources of the Nile River. The water level of Lake Victoria is determined by its water balance, consisting of precipitation on the lake, evaporation from the lake, inflow from tributary rivers and lake outflow, controlled by two hydropower dams. Due to scarcity of in-situ observations, previous estimates of individual water balance terms are characterised by substantial uncertainties, which makes that the water balance is often not closed independently. Here we present a water balance model for Lake Victoria, using state-of-the-art remote sensing Precipitation is the main cause of seasonal and inter-annual lake level fluctuations, and on average causes the lake level to rise from May to July and to fall from August to December. Finally, our results indicate that the 2004-2005 drop in lake level can be attributed about half to a drought in the Lake Victoria Basin and about half to an enhanced outflow, highlighting the sensitivity 10 of the lake level to human operations at the outflow dam.

Limnological changes in Lake Victoria since the mid‐20th century

“…The streams with the highest contribution of inflow into Lake Victoria basin are Kagera (32.7%; average daily discharge 266 m 3 /s) and Nzoia (14.6%; 119 m 3 /s) (Akurut, 2017). The water mass balance of Lake Victoria is thus largely dominated by the balance between rainfall input (+1525 mm/year) and evaporation output (−1539 mm/ year; Vanderkelen et al, 2018). The evaporative losses accounts for c. 80% of the water leaving the lake.…”

Global Heat Uptake by Inland Waters

“…For example, reservoir expansion following dam construction experienced a marked acceleration during the 1960s and 1970s, now covering 0.2% of the global land area (Lehner et al, 2011). Despite occupying <3% of the global land surface, inland waters play an important role in the climate system (e.g., Choulga et al, 2019; Subin et al, 2012; Vanderkelen et al, 2018a) and are sentinels of climate change (e.g., Adrian et al, 2009; Schewe et al, 2014). Compared to other types of land surfaces, water (i) has a higher specific heat capacity, (ii) typically has a lower albedo, (iii) allows for radiation penetration below the surface, and (iv) seasonally mixes warmer surface masses to deeper layers.…”

Comparative Analysis of Land Use/Land Cover Change and Watershed Urbanization in the Lakeside Counties of the Kenyan Lake Victoria Basin Using Remote Sensing and GIS Techniques

“…The water levels in the lake have been known to occasionally experience relative rise and falls [47]. These fluctuations could be attributed to prolonged dry seasons with high evaporation rates, and widespread massive flooding during periods of intense rainfall, especially around the plains [48,49]. The heavy rains also fill up the rivers extending their banks and causes scattered marsh pools in the basin [49].…”

“…These fluctuations could be attributed to prolonged dry seasons with high evaporation rates, and widespread massive flooding during periods of intense rainfall, especially around the plains [48,49]. The heavy rains also fill up the rivers extending their banks and causes scattered marsh pools in the basin [49]. There is also the possibility that the slight reductions in areas under water could be due to the draining and conversion of wetlands to built-up areas and agricultural farms [50].…”