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Climate change is affecting the agriculture, water, and energy sectors in East Africa and the impact is projected to increase in the future. To allow adaptation and mitigation of the impacts, we assessed the changes in climate and their impacts on hydrology and hydrological extremes in East Africa. We used outputs from seven CMIP‐6 Global Climate Models (GCMs) and 1981–2010 is used as a reference period. The output from GCMs are statistically downscaled using the Bias Correction‐Constructed Analogs with Quantile mapping reordering method to drive a high‐resolution hydrological model. The Variable Infiltration Capacity and vector‐based routing models are used to simulate runoff and streamflow across 68,300 river reaches in East Africa. The results show an increase in annual precipitation (up to 35%) in Ethiopia, Uganda, and Kenya and a decrease (up to 4.5%) in Southern Tanzania in the 2050s (2041–2070) and 2080s (2071–2100). During the long rainy season (March–May), precipitation is projected to be higher (up to 43%) than the reference period in Southern Ethiopia, Kenya, and Uganda but lower (up to −20%) in Tanzania. Large parts of Kenya, Uganda, Tanzania, and Southern Ethiopia show an increase in precipitation (up to 38%) during the short rainy season (October–December). Temperature and evapotranspiration will continue to increase in the future. Further, annual and seasonal streamflow and hydrological extremes (droughts and floods) are projected to increase in large parts of the region throughout the 21st century calling for site‐specific adaptation. Key Points: Precipitation, precipitation extremes, and temperature will increase in large parts of East Africa in the 21st centuryHydrological extremes (droughts and floods) will increase in the future in large parts of Ethiopia, Kenya, and TanzaniaSite‐specific adaptation measures are urgently required to minimize the adverse impact of hydroclimate extremes in East Africa [ABSTRACT FROM AUTHOR]

Land degradation is a major threat to food security in Sub Saharan Africa. Low infiltration rates in degraded soils increase the risk of surface runoff and decrease soil and groundwater recharge, resulting in further loss of soil fertility, water scarcity and crop failure. Increasing woody vegetation typically enhances soil infiltrability but little is known about how species may have differential effects on the soil hydrological properties. The aim of this study is to understand how woody vegetation and its functional properties affect soil fertility and infiltrability.We measured field‐saturated soil hydraulic conductivity (Kfs) and soil organic carbon (SOC) in 38 plots across agricultural landscapes in Muminji, Kenya. Woody vegetation and land use inventories took place and species functional traits were measured on the 63 most abundant species. We systematically tested the effects of vegetation quantity (aboveground woody biomass and vegetation cover) and quality (functional properties and diversity) on soil health (Kfs as a proxy for soil infiltrability and SOC for soil fertility).We found that both vegetation quantity and quality affected soil health. Aboveground woody biomass increased the Kfs and we found a nearly significant positive effect of vegetation cover on SOC. Woody plants with a low leaf thickness positively affected Kfs and a nearly significant negative effect of wood moisture content on SOC was found.Synthesis and applications. This study demonstrates that the systematic assessment of vegetation can lead to evidence‐based recommendations to guide land restoration. We found that avoiding bare soil and promoting woody plants, while favouring species with thin leaves and avoiding species with a very low wood density and water storage strategy, is beneficial for soil health across agricultural landscapes in East African drylands. [ABSTRACT FROM AUTHOR]

This study reviews Kenya's fluctuating hydroclimate (3°S–4°N, 35°–40°E) and evaluates products that describe its area-averaged daily rainfall during 2008–18, monthly evaporation during 2000–18, and catchment hydrology via gauge, satellite, and model hindcast/forecast. Using the correlation of rainfall as a metric of skill we found daily satellite versus model hindcasts achieved 75%, while model forecasts at 2–6-day lead achieved 55%–58%. The daily satellite versus model soil moisture had a significant correlation (84%), and model runoff versus gauge streamflow reached 61%. A 2-day delay was noted between rainfall and streamflow response in recent flood events; however, long-range predictability was found to be poor (35%). These outcomes were considered at a local workshop, and ways to sustainably improve the real-time reporting of key hydroclimate parameters for operational data assimilation were suggested as steps toward better monitoring and forecast services in Kenya. [ABSTRACT FROM AUTHOR]

Soda lakes are some of the most productive aquatic ecosystems. 1 Their alkaline-saline waters sustain unique phytoplankton communities 2,3 and provide vital habitats for highly specialized biodiversity including invertebrates, endemic fish species, and Lesser Flamingos (Phoeniconaias minor). 1,4 More than three-quarters of Lesser Flamingos inhabit the soda lakes of East Africa 5 ; however, populations are in decline. 6 Declines could be attributed to their highly specialized diet of cyanobacteria 7 and dependence on a network of soda lake feeding habitats that are highly sensitive to climate fluctuations and catchment degradation. 8,9,10,11,12 However, changing habitat availability has not been assessed due to a lack of in situ water quality and hydrology data and the irregular monitoring of these waterbodies. 13 Here, we combine satellite Earth observations and Lesser Flamingo abundance observations to quantify spatial and temporal trends in productivity and ecosystem health over multiple decades at 22 soda lakes across East Africa. We found that Lesser Flamingo distributions are best explained by phytoplankton biomass, an indicator of food availability. However, timeseries analyses revealed significant declines in phytoplankton biomass from 1999 to 2022, most likely driven by substantial rises in lake water levels. Declining productivity has reduced the availability of healthy soda lake ecosystems, most notably in equatorial Kenya and northern Tanzania. Our results highlight the increasing vulnerability of Lesser Flamingos and other soda lake biodiversity in East Africa, particularly with increased rainfall predicted under climate change. 14,15,16 Without improved lake monitoring and catchment management practices, soda lake ecosystems could be pushed beyond their environmental tolerances. [Display omitted] • Lesser Flamingo distributions are determined by lake productivity and water levels • Productivity has declined across East African soda lakes due to rising water levels • Flamingo distributions will likely shift north and south away from the equator • Declines in healthy soda lake ecosystems threaten their unique biodiversity More than three-quarters of the world's Lesser Flamingos feed on the cyanobacterial blooms present in the productive soda lakes of East Africa. Byrne et al. show that rising water levels are driving significant declines in soda lake productivity, reducing the habitat availability for Lesser Flamingos and other soda lake biodiversity. [ABSTRACT FROM AUTHOR]

Despite provision of preventive measures against schistosomiasis such as mass drug administration (MDA), the prevalence of Schistosoma mansoni remains high in communities living near Lake Victoria. This study aimed to analyse the status of schistosomiasis, including its prevalence, health education, knowledge, attitudes, and practices (KAP) among pupils, and water use in schools in Mbita situated along the shores of Lake Victoria. Four primary schools were selected as target schools and pupils in classes six and seven were recruited as study participants. The prevalence of S. mansoni was examined by Kato-Katz method. Simultaneously, a KAP survey toward schistosomiasis was conducted among the pupils. Health education contents were extracted from textbooks. All primary schools in the study site were surveyed regarding how each secured water used for daily school life. The prevalence of S. mansoni was 56% and 36% in 2015 and 2016, respectively. 60–70% of pupils chose a correct answer for the mode of transmission. More than 70% of pupils answered that bathing in Lake Victoria causes Schistosoma infection; however, more than 70% of pupils bathed in Lake Victoria sometimes or every day. According to the science textbook, “avoiding contact with contaminated water” is the way to prevent schistosomiasis; however, 66% of schools asked pupils to bring water from Lake Victoria. The prevalence of S. mansoni among pupils remains high. Schoolchildren are taught to avoid contact with contaminated water but are often asked to fetch water from the lake. From the school health viewpoint, health education that reflects the social and cultural context of the community in the contents and teaching methods are needed. In addition to this, provision of sanitation infrastructure is needed. A comprehensive and innovative approach which harmonises central and local governments and other stakeholders, as well as community is important to prevent schistosomiasis. [ABSTRACT FROM AUTHOR]

Water point mapping databases, generated through surveys of water sources such as wells and boreholes, are now available in many low and middle income countries, but often suffer from incomplete coverage. To address the partial coverage in such databases and gain insights into spatial patterns of water resource use, this study investigated the use of a maximum entropy (MaxEnt) approach to predict the geospatial distribution of drinking-water sources, using two types of unimproved sources in Kenya as illustration. Geographic locations of unprotected dug wells and surface water sources derived from the Water Point Data Exchange (WPDx) database were used as inputs to the MaxEnt model alongside geological/hydrogeological and socio-economic covariates. Predictive performance of the MaxEnt models was high (all > 0.9) based on Area Under the Receiver Operator Curve (AUC), and the predicted spatial distribution of water point was broadly consistent with household use of these unimproved drinking-water sources reported in household survey and census data. In developing countries where geospatial datasets concerning drinking-water sources often have necessarily limited resolution or incomplete spatial coverage, the modelled surface can provide an initial indication of the geography of unimproved drinking-water sources to target unserved populations and assess water source vulnerability to contamination and hazards. [ABSTRACT FROM AUTHOR]

Young children are infected by a diverse variety of enteric pathogens in low-income, high-burden countries. Little is known about which conditions pose the greatest risk for enteric pathogen exposure and infection. Young children frequently play in residential public areas around their household, including areas contaminated by human and animal feces, suggesting these exposures are particularly hazardous. The objective of this study was to examine how the dose of six types of common enteric pathogens, and the probability of exposure to one or multiple enteric pathogens for young children playing at public play areas in Kisumu, Kenya is influenced by the type and frequency of child play behaviors that result in ingestion of soil or surface water. Additionally, we examine how pathogen doses and multi-pathogen exposure are modified by spatial variability in the number of public areas children are exposed to in their neighborhood. A Bayesian framework was employed to obtain the posterior distribution of pathogen doses for a certain number of contacts. First, a multivariate mixed effects tobit model was used to obtain the posterior distribution of pathogen concentrations, and their interdependencies, in soil and surface water, based upon empirical data of enteric pathogen contamination in three neighborhoods of Kisumu. Then, exposure doses were estimated using behavioral contact parameters from previous studies and contrasted under different exposure conditions. Pathogen presence and concentration in soil varied widely across local (< 25 meter radius area) and neighborhood-level scales, but pathogens were correlated among distinct surface water samples collected near to each other. Multi-pathogen exposure of children at public play areas was common. Pathogen doses and the probability of multi-pathogen ingestion increased with: higher frequency of environmental contact, especially for surface water; larger volume of soil or water ingested; and with play at multiple sites in the neighborhood versus single site play. Child contact with surface water and soil at public play areas in their neighborhood is an important cause of exposure to enteric pathogens in Kisumu, and behavioral, environmental, and spatial conditions are determinants of exposure. [ABSTRACT FROM AUTHOR]

Our ability to measure household-level food insecurity has revealed its critical role in a range of physical, psychosocial, and health outcomes. Currently, there is no analogous, standardized instrument for quantifying household-level water insecurity, which prevents us from understanding both its prevalence and consequences. Therefore, our objectives were to develop and validate a household water insecurity scale appropriate for use in our cohort in western Kenya. We used a range of qualitative techniques to develop a preliminary set of 29 household water insecurity questions and administered those questions at 15 and 18 months postpartum, concurrent with a suite of other survey modules. These data were complemented by data on quantity of water used and stored, and microbiological quality. Inter-item and item-total correlations were performed to reduce scale items to 20. Exploratory factor and parallel analyses were used to determine the latent factor structure; a unidimensional scale was hypothesized and tested using confirmatory factor and bifactor analyses, along with multiple statistical fit indices. Reliability was assessed using Cronbach’s alpha and the coefficient of stability, which produced a coefficient alpha of 0.97 at 15 and 18 months postpartum and a coefficient of stability of 0.62. Predictive, convergent and discriminant validity of the final household water insecurity scale were supported based on relationships with food insecurity, perceived stress, per capita household water use, and time and money spent acquiring water. The resultant scale is a valid and reliable instrument. It can be used in this setting to test a range of hypotheses about the role of household water insecurity in numerous physical and psychosocial health outcomes, to identify the households most vulnerable to water insecurity, and to evaluate the effects of water-related interventions. To extend its applicability, we encourage efforts to develop a cross-culturally valid scale using robust qualitative and quantitative techniques. [ABSTRACT FROM AUTHOR]

In this work we explore the impact that changes in local climate and river hydrology have on the morphodynamics of a river delta, particularly focusing on the evolution of the delta generating at the lake inlet. We investigated the case of the delta in the lower reach of the Omo River in Ethiopia, which flows into lake Turkana, Kenya. The lake is the fourth largest lake and the largest desert lake in the world. This case study is of particular interest because within the last decades three dams have been built within the Omo basin. Among these, the Gibe III dam had a huge impact on the river hydrology and the sediment supply. To quantify changes in land use and river morphology and relate these to climate change and river hydrology we collated a historical dataset by combining information from different satellite sources. We observed that the amount of bare sediments progressively diminished and the biomass became denser compared to the existence of sparse biomass in the past. We argue that this is due to the changes in river hydrology and sediment load imposed by the dam, which increased sediment erosion by deepening the channel. The presence of the dam also increased the low flow level and reduced the peak flow during flood season, reducing the natural oscillations of the water table. In consequence, the possibility to plant for the local population was removed during floods. Our findings also indicate that the hydrology and reduced sediment discharge have changed the downstream (e.g. lake level), and upstream (e.g. mouth bar deposition) boundary conditions controlling the evolution of the delta structure, respectively. As a result, the delta morphology became less dynamic and less complex. • The impacts of climate, hydrology, and Gibe III dam on the River Omo delta morphodynamics are studied. • Satellite imagery analysis is used to quantify such changes and relate them to climate and hydrology. • Reduced low flows and flood peaks decreased sediment apportion causing vegetation density increase. [ABSTRACT FROM AUTHOR]

Quantification of sediment and carbon (C) fluxes in rivers with strong seasonal and inter-annual variability presents a challenge for global flux estimates as measurement periods are often too short to cover all hydrological conditions. We studied the dynamics of the Tana River (Kenya) from 2012 to 2014 through daily monitoring of sediment concentrations at three sites (Garissa, Tana River Primate Reserve and Garsen) and daily monitoring of C concentrations in Garissa and Garsen during three distinct seasons. In wet seasons, C fluxes were dominated by particulate organic C (POC) and decreased downstream. Dry season fluxes of dissolved inorganic C (DIC) and POC had a similar share in total C flux at both locations while POC fluxes increased downstream. The dissolved organic C (DOC) flux did not show strong spatial nor temporal variations. The construction of constituent rating curves with a bootstrap method in combination with daily discharge data (1942-2014) provided potential sediment and C flux ranges as a function of annual discharge. At low annual discharge, our estimates generally predict a net decrease of sediment and C storage between the upstream and downstream site. As the annual discharge increases, our simulations shift toward net retention. This analysis allowed us to infer how variations in discharge regime, related to climate or human impacts, may affect riverine fluxes. Overall, we estimate that retention was dominant: integration over all simulations resulted in an average net retention of sediment (~2.9 Mt yr-1), POC (~18000 tC yr-1), DOC (~920 tC yr-1) and DIC (~1200 tC yr-1) over the 73 years of discharge measurements. [ABSTRACT FROM AUTHOR]

The paper proposes a probabilistic approach to the assessment of the impacts of multipurpose dams. It is framed around the notion of Nature's Contributions to People (NCP) in the setting of the Water-Energy-Food nexus. The socio-ecological context of the Tana River Basin in Kenya and the construction of two multipurpose dams are used to highlight co-produced positive and negative NCP under alternative river regimes. These regimes produce both damaging floods that ought to be controlled and beneficial floods that ought to be allowed. But the river regime that results from hydropower generation and flood risk reduction may not be the one that is most conducive to food and feed-based NCP. The approach relates the economic value of river-based NCP co-production to the probability of flooding to derive the expected annual value of NCP and a NCP value-probability curve. The relation between NCP flows and flood characteristics is tested and estimated based on regression analyses with historical data. Results indicate that the net economic value of key NCP associated with multipurpose dams for local people and associated social equity effects largely depend on the frequency of flood events and on the way impacts are distributed across communities, economic sectors and time. [ABSTRACT FROM AUTHOR]

Effective integrated water resources management requires reliable estimation of an overall basin water budget and of hydrologic fluctuations between groundwater and surface-water resources. Seasonal variability of groundwater-surface water exchange fluxes impacts on the water balance. The long term lake water balance was calculated by Modflow using the stage-volume rating curve of Lake Package LAK3. The long term average storage volume change is 8.4 × 108 m³/month. The lake water balances suggests that the lake is not in equilibrium with the inflow and outflow terms. Using field abstraction data analysis and model simulation, the combined volume of lake-groundwater used for industrial abstraction since the last three decades was estimated. This requires an average abstraction amount of 7.0 × 106 m³/month with a long term trend of abstraction ratio 30% (groundwater) and 70% (lake water) since 1980. The amount resulted in a lake which might have been 4.8 m higher than was observed in the last stress period (2010). A long term regional groundwater budget is calculated reflecting all water flow in to and out of the regional aquifer. The model water balance suggests that lake Navaisha basin is in equilibrium with a net outflow about 1% greater than the inflow over the calibrated period of time (1932-2010). The regional model is best used for broad-scale predictions and can be used to provide a general sense of groundwater to surface water and groundwater to groundwater impacts in the basin. A basin wide water resource management strategy can be designed by integrating the lake/wetland within the regional groundwater model to increase the level of sustainable production and good stewardship in Lake Navaisha. Such hydrological analysis is crucial in making the model serve as simulator of the response of lake stage to hydraulic stresses applied to the aquifer and variation in climatic condition. [ABSTRACT FROM AUTHOR]

Highlights: [•] This study analyzed the irrigation potential and investment needs for Kenya. [•] The analysis considered agronomic, hydrological, and economic factors. [•] Kenya has considerable scope for expanding dam-based and small-scale irrigations. [•] The study provided a strategic prioritization for investments in irrigation schemes. [ABSTRACT FROM AUTHOR]

Highlights: [•] A 3D ground water flow model is used to simulate the lake aquifer interaction. [•] A DEM with 30 m resolution was used to improve the 3-D representation of the lake. [•] The lake is considered as a high hydraulic conductivity in the modeling framework. [•] The simplicity of the model approach can be implemented with existing preprocessor. [•] The calibration process was carried out using pilot points and regularization. [ABSTRACT FROM AUTHOR]

The spatio-temporal changes in the land cover states of the Nyando Basin were investigated for auxiliary hydrological impact assessment. The predominant land cover types whose conversions could influence the hydrological response of the region were selected. Six Landsat images for 1973, 1986, and 2000 were processed to discern the changes based on a methodology that employs a hybrid of supervised and unsupervised classification schemes. The accuracy of the classifications were assessed using reference datasets processed in a GIS with the help of ground-based information obtained through participatory mapping techniques. To assess the possible hydrological effect of the detected changes during storm events, a physically based lumped approach for infiltration loss estimation was employed within five selected sub-basins. The results obtained indicated that forests in the basin declined by 20% while agricultural fields expanded by 16% during the entire period of study. Apparent from the land cover conversion matrices was that the majority of the forest decline was a consequence of agricultural expansion. The model results revealed decreased infiltration amounts by between 6% and 15%. The headwater regions with the vast deforestation were noted to be more vulnerable to the land cover change effects. Despite the haphazard land use patterns and uncertainties related to poor data quality for environmental monitoring and assessment, the study exposed the vast degradation and hence the need for sustainable land use planning for enhanced catchment management purposes. [ABSTRACT FROM AUTHOR]

Some of the most valued natural and cultural landscapes on Earth lie in river basins that are poorly gauged and have incomplete historical climate and runoff records. The Mara River Basin of East Africa is such a basin. It hosts the internationally renowned Mara-Serengeti landscape as well as a rich mixture of indigenous cultures. The Mara River is the sole source of surface water to the landscape during the dry season and periods of drought. During recent years, the flow of the Mara River has become increasingly erratic, especially in the upper reaches, and resource managers are hampered by a lack of understanding of the relative influence of different sources of flow alteration. Uncertainties about the impacts of future climate change compound the challenges. We applied the Soil Water Assessment Tool (SWAT) to investigate the response of the headwater hydrology of the Mara River to scenarios of continued land use change and projected climate change. Under the data-scarce conditions of the basin, model performance was improved using satellite-based estimated rainfall data, which may also improve the usefulness of runoff models in other parts of East Africa. The results of the analysis indicate that any further conversion of forests to agriculture and grassland in the basin headwaters is likely to reduce dry season flows and increase peak flows, leading to greater water scarcity at critical times of the year and exacerbating erosion on hillslopes. Most climate change projections for the region call for modest and seasonally variable increases in precipitation (5-10%) accompanied by increases in temperature (2.5-3.5 °C). Simulated runoff responses to climate change scenarios were non-linear and suggest the basin is highly vulnerable under low (-3%) and high (+25%) extremes of projected precipitation changes, but under median projections (+7%) there is little impact on annual water yields or mean discharge. Modest increases in precipitation are partitioned largely to increased evapotranspiration. Overall, model results support the existing efforts of Mara water resource managers to protect headwater forests and indicate that additional emphasis should be placed on improving land management practices that enhance infiltration and aquifer recharge as part of a wider program of climate change adaptation. [ABSTRACT FROM AUTHOR]

Tindiret natural forest is one of the scattered forests which form the extensive Mau forest complex in Kenya. It is an important hydrological system for Lake Victoria. To provide strong arguments for more government investment in indigenous forest conservation, quality information and data on forest values need to be available for decision makers. There is, however, little information on economic values of most forests in Kenya. This study was aimed at estimating the total economic value of Tindiret forest. To estimate direct use values by the communities adjacent to the forest, household surveys were conducted with 109 households sampled from three villages within 5 km of the forest. Further information was obtained from discussions with key informants. The methods employed were market-based valuation techniques, market valuation of physical effects (MVPE) and use of secondary data and benefit transfer approach. The study established that the annual direct use value by local forest-adjacent households was approximately Kshs45 mil. The non-use values were estimated at Kshs113 mil per year and the opportunity cost of conserving the Tindiret natural forest was estimated at Kshs237 mil. Current benefits from Tindiret forest are inadequate to offset the opportunity cost of leaving the forest in its present state. The government and the local communities are subsidising the retention of the forest and this subsidy was estimated at Kshs78.5 mil per year through lost opportunity in agricultural settlement and income. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to evaluate the impact of climate change on streamflow using the Soil and Water Assessment Tool (SWAT) model. It presents the analysis performed on the Nzoia catchment in the Lake Victoria basin in Kenya, and the significance of the changes in temperature and precipitation detected by the global circulation models (GCMs). It also offers insights on surface runoff, base flow, probability of flood and the world's water resources.

Abstract: The Late Pleistocene to Middle Holocene African Humid Period (AHP) was characterized by dramatic hydrologic fluctuations in the tropics. A better knowledge of the timing, spatial extent, and magnitude of these hydrological fluctuations is essential to decipher the climate-forcing mechanisms that controlled them. The Suguta Valley (2°N, northern Kenya Rift) has recorded extreme environmental changes during the AHP. Extensive outcrops of lacustrine sediments, ubiquitous wave-cut notches, shorelines, and broad terrace treads along the valley margins are the vestiges of Lake Suguta, which once filled an 80km long and 20km wide volcano–tectonic depression. Lake Suguta was deep between 16.5 and 8.5calkaBP. During its maximum highstand, it attained a water depth of ca 300m, a surface area of ca 2150km2, and a volume of ca 390km3. The spatial distribution of lake sediments, the elevation of palaeo-shorelines, and other geomorphic evidences suggest that palaeo-Lake Suguta had an overflow towards the Turkana basin to the north. After 8.5calkaBP, Lake Suguta abruptly disappeared. A comparison of the Lake Suguta water-level curve with other reconstructed water levels from the northern part of the East African Rift System shows that local insolation, which is dominated by precessional cycles, may have controlled the timing of lake highstands in this region. Our data show that changes of lake levels close to the Equator seem to be driven by fluctuations of spring insolation, while fluctuations north of the Equator are apparently related to variations in summer insolation. However, since these inferred timings of lake-level changes are mostly based on the radiocarbon dating of carbonate shells, which may have been affected by a local age reservoir, alternative dating methods are needed to support this regional synthesis. Between 12.7 and 11.8calkaBP, approximately during the Northern Hemisphere high-latitude Younger Dryas, the water level of Lake Suguta fell by ca 50m, suggesting that remote influences also affected local hydrology. [Copyright &y& Elsevier]

The Mara River is the lifeline of the transboundary Mara basin across Kenya and Tanzania. The basin is considered one of the more serene subcatchments of the Lake Victoria Basin and ultimately the Nile Basin, and traverses the famous Maasai Mara and Serengeti National Parks. The basin also contains forests, large-scale farms, smallholder farms, pastoral grazing lands, as well as hunter gatherers and fishers. There is growing concern, however, regarding land degradation in the basin, particularly deforestation in the headwaters, that is affecting the natural resource base and the river flows. Accurate scientific data are required to advise policy, and to plan appropriate mitigation measures. This study utilizes remote sensing and geographical information system (GIS) tools, and hydrological and ground-truth studies to determine the magnitude of the land-use/cover changes in the Mara River Basin, and the effects of these changes on the river flows over the last 30 years. The study results indicate that land-use/cover changes have occurred. In 1973, for example, rangelands (savannah, grasslands and shrublands) covered 10 989 km2 (79%) of the total basin area. The rangelands had been reduced to 7245 km2 (52%) by 2000, however, while the forest areas were reduced by 32% over the same period. These changes have been attributed to the encroachment of agriculture, which has more than doubled (203%) its land area over the same period. The hydrology of the Mara River also has changed, with sharp increases in flood peak flows by 7%, and an earlier occurrence of these peaks by 4 days between 1973 and 2000. There is evidence of increased soil erosion in the upper catchments, with silt build-up in the downstream floodplains. This has caused the Mara wetland to expand by 387%, adversely affecting riparian agriculture. There is need for urgent action to stem the land degradation of the Mara River Basin, including planning and implementing appropriate mitigation measures. [ABSTRACT FROM AUTHOR]

The hydrodynamics and the long-term water balance of two topographically closed crater lakes is presented in a comparative manner using a spread-sheet hydrological model. The main objective of the work is to study the role of groundwater and the effect of water abstraction from lakes Awassa and Naivasha. The rationale of selection of the two lakes separated by thousands of kilometers is the striking similarity of their hydrogeological and geomorphological setting and future intended water uses for large-scale abstraction from the lakes and feeder rivers. The net groundwater outflow from Lake Awassa and the effect of water abstraction from Lake Naivasha under different scenarios were calculated based upon the average monthly hydrometeorological data of rainfall, evaporation and river inflows. The net groundwater flux was obtained from the simulation as a residual of other water balance components and was found to be substantial in both lakes. The result revealed that the annual net groundwater outflow from Lake Awassa to adjacent basins is estimated at 58 ×106 m³. The predicted and recorded lake levels fit well for much of the simulation period. For Lake Naivasha groundwater flows into and out of the lake are successfully estimated based on the predicted water level fluctuations when water abstraction was at a minimal. The most accurate predictions of lake level were derived from the data sets of river discharges known to be from the most-reliable time period after the early 1970s. The model estimated an annual abstraction rate and groundwater outflow from Lake Naivasha of 60×106 m³ and 56×106 m³ respectively. The model demonstrated its validity as a good management tool to predict effects of large-scale pumping and extreme climatic events that may affect the lakes in space and time. [ABSTRACT FROM AUTHOR]

Loboi Swamp is a 1.5 km² freshwater wetland situated near the equator in the Kenya Rift Valley. The climate is semi-arid: precipitation is ≈700 mm year-1, and evapotranspiration is ≈ 2500 mm year-1. Some of the wetland water is currently used for irrigation. An interdisciplinary study was conducted on the geology, hydrology, pedology and biology of the wetland to determine its origin and history and to assess its longevity under present hydrological conditions. Sedimentary records from two piston cores (1.8 and 4 m long) indicate that the present wetland developed during the late Holocene on a low-relief alluvial plain. Floodplain deposits (sandy silts) are capped with wetland sediments (organic-rich clay and peat), which began to form at ≈700 BP. The swamp is dominated by Typha domingensis Pers. (≈80%) and floating Gyperus papyrus L. (20%). It is fed by warm springs (T ≈ 35 °C; pH ≈ 6.4-6.9) emanating from grid faults of the rift floor. Water compositions suggest that sources are dominated by shallow meteoric water, with little contribution from deeper geothermal fluids. Siderite concretions in the floodplain silts reflect the Fe-reducing conditions that developed as the surface became submerged beneath the water table. The pollen record captured both local and more regional vegetation, showing the prevailing dry rift valley climate despite development of the wetter conditions on the valley floor. The diatom record also suggests a dramatic change in local hydrology. The combined biological records of this semi-arid wetland indicate an abrupt change to wetter conditions, most probably as a result of a regional change in climate. Rift tectonics provided accommodation space, maintained the wetland at or below the water table and enabled spring recharge. The size of the modern wetland has been reduced by about 60% since 1969, which suggests that the system may now be under hydrological stress due to anthropogenic impacts from land-use change. [ABSTRACT FROM AUTHOR]

Sustainable development remains a pressing priority for the Lake Naivasha Ramsar site, as a matter both of long- term protection of the lake ecosystem and of the economic and social progress that depends upon it. This must be addressed at catchment-scale to protect the `ecosystem services' that constitute the region's primary resources. Sustainability principles highlight energy, fertilisers, pesticides and other aspects of chemical use, plastics, erosion and sedimentation, wildlife, water and socio-economic issues as central to sustainable development strategy, influenced by both intensive and subsistence farms across the catchment. Market forces and long-term self-interest provide compelling arguments for sustainable development, the delivery of which will depend upon education and the spreading of good practice, perhaps backed up by stewardship schemes. Alternatively, the adverse consequences of continued unsustainable practice are highly significant for the region. [ABSTRACT FROM AUTHOR]

Daily pre-dam and post-dam discharge data for Kenya''s largest river, the Tana, were analysed using flood frequency analysis and computation of various indicators of hydrologic alteration (IHA). Results from these analyses indicated statistically significant (p<00·01) augmentation of minimum river flows and reduction in peak flows. We also estimated the frequency of flooding of 71 vegetation sample plots located on various parts of the river floodplain by running a hydrologic water profile simulation program (HEC-RAS). Results from these analyses indicated that plots at elevations greater than 1·80 m above the dry season river level experienced statistically significant (p<0·01) reduction in days flooded from the pre- to the post-dam period. This documented magnitude of change in the hydrologic regime will have a negative impact on the unique riverine forest occurring along the Tana River. [Copyright &y& Elsevier]

Studies the influence of hydrology on the structure of invertebrate communities in two streams flowing into Lake Nakuru, Kenya. Flow regimes of the two streams; Differences in invertebrate abundance and number of the two streams; Other factors that affected the invertebrate abundance.

As climate change adaptation is becoming a recognized policy issue, the need is growing for quantitative economic evaluation of adaptation-related public investment, particularly in the context of climate finance. Funds are meant to be allocated not to any types of beneficial investments with or without climate change but to projects regarded as effective for climate change adaptation based on some metrics. But attempts at such project-specific evaluation of adaptation effects are few, in part because such assessments require an integration of various types of simulation analyses. Against this background, we conduct a case study of a Kenyan irrigation development project using a combination of downscaled climate data, runoff simulations, yield forecasting, and local socioeconomic projections to examine the effects of interventions specifically attributable to climate change adaptation, i.e., how much irrigation development can reduce the negative effects of climate change in the future. The results show that despite the uncertainties in precipitation trends, increased temperatures due to climate change have a general tendency to reduce rice yields, and that irrigation development will mitigate income impacts from the yield loss-for example, for the median scenario, the household income loss of 6% in 2050 due to climate change without irrigation development is flipped to become positive with the project. This means that the irrigation development project will likely be effective as a means for climate change adaptation., Competing Interests: The authors have read the journal's policy and have the following competing interests: DO and AM are paid employees of commercial engineering company, Nippon Koei Co. (https://www.n-koei.co.jp/english/). There are no patents, products in development or marketed products associated with this research to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

In order to assess the sustainability and impact of production from geothermal reservoirs on hydrological systems, a thorough understanding of local and regional hydrogeological systematics is a prerequisite. The Menengai Caldera in the Kenya Great Rift Valley is one of the largest explored geothermal fields in the country. This paper presents a hydrochemical investigation of the Menengai Caldera geothermal field and the ground and surface waters of the surrounding Nakuru County. Our results demonstrated a similar, sodium-alkaline dominated, ionic composition across all water types. Geothermal wells return the highest cation/anion concentrations and largely demonstrate a meteoric source from their δ18O and δ2H signature. Wells MW-09 (central part of the caldera), MW-18 (eastern part) and MW-20 (central part) showed a more evaporitic signature, closely matching with our own calculated Lake Evaporation Line, suggesting an increased mixing influence of Lake Nakuru waters. MW-09 also showed evidence of high-temperature oxygen isotopic exchange and significant water-rock interaction. Lake samples largely demonstrated seasonal shifts in ionic and isotopic values. Lake Nakuru ionic composition and isotopic values increased throughout the 12-month wet–dry–wet season sampling period. This correlated with a decrease in area which suggests a lessening of water inflow and facilitates increased evaporation. Groundwaters demonstrated clear evidence of mixing between meteoric, irrigation and lake waters. These observations enhanced the understanding of the hydrological system surrounding the Menengai Caldera and, when combined with future studies, will provide a powerful tool to assess the sustainability and impact of soon-to-be completed geothermal power production operations. [ABSTRACT FROM AUTHOR]

Stable oxygen isotopes of hominin enamel carbonate (δ(18)OEC) provide a window into aspects of past drinking behavior and diet, body size, breastfeeding and weaning, mobility, and paleoclimate. It is tempting to compare all hominins across time and space in order to gauge species-level adaptations to changing environments and niche separation between those living sympatrically. Basinal, sub-basinal, and micro-environmental differences, however, may exert an influence on variation in enamel carbonate isotopic values that must be reconciled before hominin species across Africa can be meaningfully compared. Plio-Pleistocene Turkana hominin δ(18)OEC values show a considerable spread, potentially revealing many intrinsic and extrinsic contributing factors operating on different scales. In this study, I examine Turkana hominin δ(18)OEC values relative to identity (taxon, tooth type and number, body size of taxon), dietary (δ(13)C value, Turkana coeval and modern mammalian δ(18)OEC values), and contextual (time, depositional environment) information of each specimen and collection locality and discuss various potential influences. Turkana hominin δ(18)OEC values may primarily reflect differences in imbibed water sources (lake vs. river) as a function of evolving basin hydrology., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Web search engine Google''s new philanthropic division, Google.org, is to support research in western Kenya to identify ways to prevent child deaths caused by poor water quality and to better understand what works in rural water supply. [Copyright &y& Elsevier]

This paper highlights the use of a conceptual method for separating runoff components in daily hydrographs, contrary to the traditionallyused graphical method of separation. In the conceptual method, the components, viz. surface flow, interflow and baseflow, are regarded ashigh, medium and low frequency signals and their separation is done using the principle of a recursive digital filter commonly used in signal analysis and processing. It requires estimates of the direct runoff (Betad) and surface runoff (Betas) filter parameters which are obtained by a least-squares procedure involving baseflow and interflow indices based on graphical and recursive digital filter estimation techniques. The method thus circumvents the subjective element associated with the graphical procedure of hydrograph separation, in which case the eye approximation and/or one's skill at plotting is the prime basis for the whole analysis. The analysis based on three forest catchments in Kimakia, Kenya, East Africa, revealedthat Betad=Kb and Betas=Ki, where Kb and Ki are the baseflow and interflow recession constants. [ABSTRACT FROM AUTHOR]