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The water supply system in Kisii municipality faces many challenges. The municipality is located within the Nyakomisaro sub catchment and the water supply relies heavily on the River Nyakomisaro. The water supply system is dilapidated and there is a lot of wastage due to poor maintenance. The state of the catchment does not permit all year round supply due to degradation and climatic variability and this compromises sub-catchment integrity, given the ever rising population and increasing human activities. This study investigated challenges for water supply and stream flow management using stream flow and rainfall data from the hydrometric network and structured questionnaires for water supply and storm water management in the sub catchment. Analysis was done using standard statistical methods. When dry spells last for a week, severe water shortage causes people to travel long distances in search of it and is generally expensive thereby limiting domestic and commercial activities. Dumping of solid waste along the river, road and house construction sites affect river flow. Fish farming and eucalyptus trees along the river diminish the flow. There are no proper drainage systems in the Nyakomisaro sub catchment. Reliance on river water could be reduced by rainwater harvesting yet also flooding and poor sanitation affect water supply and ecosystem management. To improve on the water supply and drainage systems, planning for water management in the sub catchment should incorporate all stakeholders including: NEMA, GWASCO and WRMA and the community.

ASALs in the tropics present challenges to sustainable livelihoods that include drought vagaries, changing land uses, population increase, water insecurity due to rising demands and quality deterioration, as well as environmental degradation leading to declining agricultural productivity and food security. Climate change and transboundary conflicts give rise to governance challenges in water resource management of the ASALs in the tropics, and knowledge of the hydrologic processes would be critical in policy and stakeholder engagement. This chapter discusses the various aspects pertaining to the pertinent hydrological processes crucial for sustainable resource planning and development in watersheds in the tropics and also proposes best management practices including rainwater harvesting that would ensure sustained information and data for improved livelihoods in ASALs.

ASALs in the tropics present challenges to sustainable livelihoods that include; drought vagaries, land use/change, and increasing population with inherent water supply demands and vulnerability to pollution. Water insecurity, environmental degradation and declining agricultural productivity are threats to livelihoods. Climate change impacts on water resources and transboundary conflicts make resource management a daunting task. Knowledge on hydrologic processes of recharge, erosion and pollution and; climate change informs policy and stakeholder engagement. This chapter outlines the ASAL characteristics, rainwater harvesting techniques and gives insight on transboundary issues. It concludes that sustainable resource planning and development can be achieved through stakeholder engagement and multidisciplinary activities best carried out in watersheds. Planning based on information and data could yield improved livelihoods in ASALs.

Drought is a recurring hazard which affects many parts of Kenya. In most countries in Sub-Saharan Africa, agriculture which is predominantly rain-fed is the main stay of the economies is highly prone to the impacts of drought which, whenever it occurs, leads to serious socioeconomic challenges at various levels. The study of drought duration, magnitude and severity have relevance in many areas such as waste load allocations, issuance of pollution discharge permits, location of treatment plants and sanitary landfills, determination of allowable water transfers and withdrawals both within, between and outside the affected areas and determination of minimum downstream release requirements for hydropower water supply, cooling plants and other facilities. Knowledge of the frequency distribution of the drought events is useful as it contributes to the assessment of drought risks which have implications on the long term ecological, economic and social well being of the biological and human communities that make use of water from the various streams in a basin. In this study five frequency distributions were fitted to drought duration and severity as determined from discharge data from representative river gauge stations in the upper Tana Basin of Kenya. The frequency distributions fitted to the two drought events were the Generalized Normal (GN) or 3-parameter Lognormal, Generalized Extreme Value (GEV) or the Extreme Value Type III, Generalized Pareto (GPA), Pearson Type III (P3) and Generalized Logistic (GL). The distributions of best fit for the drought events were identified using the Z value obtained from the average L-moment statistics of a particular candidate distribution and the average L-moment statistics. The Z value for each homogenous region was determined from sample estimates of Lcv , Lcs and Lck that were determined from probability weighted moment estimators and the weighted means of Lcv, Lcs and Lck using records from the river gauging stations representing each hydrologically homogenous region. A frequency distribution of best fit was selected if ׀Z Dis ׀ ≤ 1.64 and the one with the lowest ׀Z Dis ׀ value selected as the distribution

Degradation of watersheds and diminishing water resources lead to unsustainable environmental and socio- economic development. The hydrological characteristics are desirable for sustainable water resource exploitation. Hydrological and water resources research were examined in three case watersheds in Kenya leading to the need for integrated water resources management, environmental conservation, and watershed management plans as a result of the major challenges of climate change and variability and uncoordinated watershed resource utilization. Well-managed hydro-meteorological networks at different scales of hydrological systems have been proposed to assess potential for optimal resource use and harmony involving all stakeholders for reduced water stress and future water conflicts. Updates of information and methodologies for watershed management that emphasize collaborative efforts and use of sustainable best practices would require input of various stakeholders including Water Resources Management Authority (WRMA), Basin Authorities, and National Environmental Management Authority (NEMA).

The purpose of this study was to establish the water resources of thenon-perennial streams in providing supplementary water needs inLaikipia district. This district has undergone remarkable land usechanges resulting in water use stress of perennial river abstractions andgroundwater exploitation in the semi arid environment.

An assessment of suspended sediment transport was carried out in a number of semiarid catchments during flood events in order to quantify the degradation rates. In order to quantify these, a systematic sampling procedure of the episodic flood events was proposed for representative catchments. The procedure allows for an integration over the whole run-off episode using both the rising and falling limbs of the run-off hydrograph to compute the sediment quantities for each individual flood event.Higher sediment concentrations occurred in the rising limb than those at the recession for any stage of flow. The maximum suspended sediment concentration was observed at the peak of the flood hydrograph. An integration of the sediment concentration over its duration gave the total sediment yield from the flood event. For the ephemeral channels, only a small number of flood events were observed over a three-year experimental period each with a duration of the order of 3-6 h. It is notable that high sediment loads were associated with high flow volumes which were effectively the result of the catchment characteristics and incident rainfall causing the flood events in the respective catchments. A large percentage of the annual sediment yield from a catchment is transported by the ephemeral streams during a small number of flood events. The correct determination of the total sediment yield from any of the flood events depends entirely on the accuracy of the measurements.The understanding of run-off and sediment loss for the representative catchments aims at assisting planning, management and control of water and land resources for sustainable development in the semi-arid parts of the tropics. The sediment rates reveal the degradation of catchments which have repercussions on the crop and pasture production and this has a bearing on the soil and water conservation programmes in the delicate ecological balance of the semi-arid areas. Further, these rates will determine the lifespan of the reservoirs planned for the dry river valleys (ephemeral streams) and existing ones which serve livestock and domestic needs. These occasionally will require costly rehabilitation and scooping to increase effective storage unless conservation measures are taken, and these measures are bound to vary from place to place as per the representative catchments output.

Stream-flow measurements are important for water resources assessment and management. In Kenya, inadequate streamflow data poses a major challenge to water resources assessment and management. Application of rainfall-runoff models to the catchments can be used to generate streamflow data. A lumped conceptual rainfall-runoff model IHACRES was applied to six medium sized catchments in the Upper Tana River Basin of Kenya. The model IHACRES was chosen because it requires only catchment area, streamflow data and a surrogate variable representing evaporation such as temperature. In addition, it has only two parameters to be varied during calibration. Streamflow data for the six catchments spanning six years was used in the present study. Simulated streamflow was compared with the observed streamflow for these catchments and the goodness of fit evaluated. The calibration R2 ranged from 0.57 to 0.85 while the simulation R2 ranged from 0.55 to 0.77 for all catchments. The Nash-Sutcliffe (1970) efficiency ranged from 0.78 to 0.91 for calibration and from 0.77 to 0.88 for simulation. Sensitivity tests were also carried out using results for one of the catchments. IHACRES is capable of simulating daily streamflow given concurrent daily rainfall and temperature data and offers a possibility of infilling missing data or generating a long series of streamflow data for water resources management in the Upper Tana River basin

IHACRES, a lumped conceptual rainfall-runoff model, was calibrated to six catchments ranging in size from 49km2 to 600 km2 within the upper Tana River basin to obtain a set of model parameters that characterise the hydrological behaviour within the region. Physical catchment attributes indexing topography, soil and land use were derived from spatial data using GIS. Equations were developed which related the conceptual parameters to catchment characteristics and which enabled the estimation of model parameters from catchment characteristics. The estimated hydrological model parameters were used to simulate stream flows in two validation catchments within the same region. Although the results varied, the stream flows simulated using the derived regional parameter sets agreed well with the observed stream flow series. The R2 values were 0.21 and 0.67 while the Nash-Sutcliffe efficiency values were 0.21 and 0.68 respectively. The results indicated that the method is viable and can be used to extend existing stream flow data in ungauged catchments or to generate data where none exists.