Qualifier Seminar by Mr. Vincent Omondi Odongo

Dept. of Urban and Regional Planning and Geo-Information Management

"Quantifying the effect of land use/cover change on water quantity and quality in Lake Naivasha Basin"

Understanding the interactions between terrestrial ecosystems and the atmosphere are fundamental in addressing issues of climate change and environmental degradation. However, quantifying these dynamic interactions both in space and time are compounded by challenges. Specifically, elucidating the impacts of land use and land cover (LULC) at the local to regional scales on surface radiation budgets, surface hydrology, surface energy balance and surface roughness are not straightforward but rather complex to warrant any generalizations. Subsequently, many insights into consequences of LULC on hydrology have been investigated at small spatial, observable scales. However, extrapolating findings from such small scales to larger scales such as river basins is confounded by the diversity of LULC as well as hydrological systems. Not only does the diversity in LULC complicate such a study, but also quantifying the effect of LULC changes of less than 20% have been empirically stated as not discernible from hydrometric measurements alone. The Lake Naivasha Basin qualifies as one such basin where dynamics in LULC changes on hydrology may not be discernible using hydrometric measurements. Hence to investigate this, the present study will adopt three techniques; (1) Statistical methods (2) Hydrological Modelling and (3) Earth observation (EO) techniques. Statistical approaches will be used to analyze time series of hydrological data to identify the time of changes, test the homogeneity of the data, link LULC and catchment characteristics to water quality and reconstruct stream flows. Reconstruction of stream flows is a necessary undertaking in order to pre-determine flows under natural conditions, the output of which will be used to quantify impacts of human induced abstractions against observed stream flows. Hydrological modelling will then be used to quantify the impact of climate variability and LULC changes on the hydrological regime of the catchment. This is important so as to account for the effect of climate signal which masks quantification of LULC effects. The third part of the study will entail the quantification of evapotranspiration (ET) using EO techniques. The spatio-temporal distribution of ET is needed for sustainable management of water resources as well as for a better understanding of water exchange processes between the land surface and the atmosphere. Considering that this work is an integral part of a larger Earth Observation Integrated Assessment (EOIA) project for Lake Naivasha Basin, it will contribute to the existing challenges linking LULC dynamics and catchment hydrology and more specifically unravel the understanding of the interface between LULC/climate and water required to undertake adaptation strategies in Lake Naivasha Basin. Finally, the study outputs will contribute to and/or link with other ongoing components in the EOIA (i.e. Ecology, Limnology, Socio-economic and Water Governance) project.

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