Streamflow and Salt Flux in Seasonal Rivers: The Case of the Semi-Arid Tiva River Basin, Kenya

This paper presents the results of a study on the influence of streamflow variability on salinity, total dissolved solids (TDS) and conductivity in a semi-arid Tiva River Basin in Kenya. Measurements of salinity, TDS, conductivity and river discharges were undertaken in sampling stations by applying standard hydrologic methods. The mean and maximum river discharges for the sub-basins of the river ranged from 11 to 33 m3s-1 and from 118 to 210 m3s-1, respectively, with the peak river discharge at the main Tiva  branch being 270 m3s-1.  The study shows that there is a significant relationship between the variability of streamflow and the variability of salinity, conductivity and TDS in the river. The relationships between streamflow and salinity were best represented by power functions rather than linear regression functions. The relationships were negative so that the levels of salinity, conductivity and TDS decreased with an increase in river discharge.  Salinity, TDS and conductivity were also inversely correlated to turbidity. An increase in turbidity corresponded to a decrease in conductivity and hence salinity and TDS. The low conductivity at high streamflow conditions were attributed to the dilution effect of increased volume and also by the presence of high proportion of non-conductance organic and inorganic materials such sand and clay.  The highest TDS, conductivity and salinity values were measured during the low flow (baseflow) conditions and the concentrations were lowest during high streamflow conditions. It is postulated that the high concentrations were a result of high evapotranspiration and seepage of subterranean water from bank storage and groundwater aquifers, and that low concentrations were a result of dilution and flushing effect of high streamflow. Inter-subbasin variations in the levels of salinity were attributed to differences in landuses, lengths and sizes of the sub-basins. The effects of upstream irrigation were evident in one of the main sub-basins-Mwitasyano river where the highest salinity levels (max: 3.4%; mean 1.1%) were measured. The total salt flux from Upper Tiva river basin was estimated to be 100,344 tonnes.yr-1 with basin salt production rate of 27.87 tons.m-2.yr-1. This salt flux was attributed to the nature of the basement complex metamorphic rocks (e.g. Kankur limestone) through which the river drains. The influence of irrigation upstream was noted to be important in the Mwitasyano sub-basin that contributed 61% of the total salt load. The study emphasizes the need for water resources and agricultural development programmes in the semi arid Tiva River Basin to promote sustainable irrigation and landuse practices. It is suggested that construction of water reservoirs in the Tiva basin would help in controlling salinity levels in the river. Keywords: Tiva River; Salinity; Total Dissolved Solids (TDS); Streamflow; Salt fluxes; Keny

Seasonal river channel water exchange and implications on salinity levels in sand dams: Case of semi-arid Kitui Region, Kenya

This paper presents results of a study on the variations of salinity levels (and associated physico-chemical parameters) in sandbeds of seasonal rivers found in the semi-arid region of Kenya. The study sought to investigate the interaction between water in river sandbeds and bank storage and how this interaction influences salinity levels in sand dams and shallow wells in semi arid lands. The results of the study show that there is a significant relationship between water quality parameters in dry river sandbeds and the corresponding water quality parameters in shallow wells and sand dams. Within river sandbeds, the dry season salinity ranged from 0.9 to 12.8% while the wet season salinity ranged from 0.4 to 1.1%. The wet season total dissolved solids (TDS) concentrations ranged from 77.8 to 272 mgl-1. The dry season TDS concentrations were high ranging from 227 to 3,320 mgl-1. The wet season water conductivities were  however low ranging from 155.9 to 539 µS.cm-1 as compared to the dry season conductivities that were high ranging from 455 to 6,640 µS.cm-1. As compared to the river channel sandbeds, water in shallow wells and sand dams was characterized by relatively high levels of physico-chemical parameters with salinity ranging between 1.5% and 6.5% and TDS concentrations ranging from 396 to 1,680 mgl-1. The level of salinity in sand dams and shallow wells tends to be much higher than those in the stream channel sandbed. Also, within the river channel sand beds, the levels of salinity were mostly within the minimum allowable limit for drinking water except in extended drought periods. The relatively high salinity, TDS concentrations and conductivity were attributed to mineralization of water due to entrapment, ground water recharge and solubisation of minerals from soils. The study shows that the flow of water within sand bed matrix is characterized by low hydraulic conductivities and water fluxes and this has important implication on the salinity levels in sand beds of seasonal rivers.   Keywords: Sandy river channel; water exchange; bank storage; salinity; Kitui, Kenya

The Study of the Effects of Mau Catchment Degradation on the Flow of the Mara River, Kenya

There is growing concern however, regarding land degradation in the Mara River Basin in Kenya, particularly deforestation in the headwaters; that is affecting the natural resource base and the river flows. Scientific studies are required to advise on policy issues, and to plan appropriate mitigation measures in the basin. This study utilized 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 results of the studies indicate that land-use/cover changes have occurred in the basin. In 1973, for example, rangelands (savannah, grasslands and shrublands) covered 10,989 km2 (79%) of the total basin area. The rangelands have now been reduced to 7,245 km2 (52%) by 2000. The forest areas have been 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. To investigate the effects of land cover change on river flow, stream flow was generated from derived land cover thematic maps of 1973 and 2000 using the same rainfall and evaporation data of 1983 to 1992 period. The  other  model  input  datasets  for  topography  and  soils  were  held  constant during the two runs. The differences in the generated hydrographs could only be associated to the changes in land cover, which was the only variable. The percentage difference between the mean annual stream flows of the two hydrographs was negligible at 0.01%. This study therefore  concludes  that  land  cover  changes  in  the  basin  have changed the day to day flow characteristics of the  Mara river but the annual flow volumes remain unaffected. There is need for urgent action to stem the land degradation of the Mara River Basin, including planning and implementing appropriate mitigation measures. Keywords: SWAT model, Mara River Basin, Hydrological Modelling, River Discharge

Sand Gradation in Seasonal Rivers and Their Suitability for Construction of Sand Dams in Kitui South, Kenya

This study was undertaken in Kitui South in Kitui County in the south eastern parts of Kenya. The main objective of the study was to develop a spatial model that can be used for selection of suitable sites for sand dam in Kitui South. The study also assessed the spatial variation of sand grain sizes and how these determines the suitability of sites for the sand dams. Data analysis was done using three approaches. The first approach involved the use of the Remote Sensing (RS) technique where data was preprocessed and analyzed using Erdas Imagine software and Geographical Information Systems (GIS) for spatial modelling. The distribution of sand particle-sizes was based on sieve analysis on the sand samples collected from seasonal rivers in the study area. The seasonal rivers that were investigated in this study included Mwila, Kakya, Wiitu, Nguni, Ngunyumu, Muvuko, Kanzilu, Masaa, Katiliku, Ngulungu, Nzeeu, Koma and Katitika. Statistical analysis was done to establish the relationships between the various spatial components affecting sand particle distribution. The results from the spatial model which integrated all factors shows that 16% of the studied sites along the seasonal rivers in Kitui South were fairly suitable for construction of sand dams while 79% were classified as suitable and 5% are categorized as very suitable. Several sites in the central and the entire eastern parts of Mutha Ward were found not suitable for sand dam construction due to poor conditions such as the lack of suitable sand particles, lack of bedrock exposure on the riverbeds, flat terrain, very shallow stream banks, and weak soils on the riverbanks. Suitable sites for sand dams were found on the western and central areas of Kitui South where production and high accumulation of coarse sands was observed along the seasonal rivers. The areas near Mutomo hills and the rocky areas in Ikanga wards were found to be characterized with few excellent sites for sand dams. The optimum accumulation of different grades of sand in the seasonal rivers was found on streams with slope of between 1.5 and 6% that were dominated with0 to 40% coarse sands, 0 to 30% fine gravels, 0 to 20% fine sands, and 20 to 80% medium sands. The accumulation of fine gravels was found to be closely related to the distribution of D30, D60 and D90sand particle-sizes (0.4-4mm) while accumulation of coarse sands showed good relationship with the distribution of the medium size sand (0.2-0.4mm). The accumulation of medium sands was equally high when the occurrence of coarse sands was minimal. Different grades of sand were found to be strongly influenced by the changes in the elevation of the stream especially with regard to the accumulation of the medium sands (r= 0.76) and coarse sands(r=0.75). Out of 80 investigated sites, 59% of them were dominated with uniform sands (Cu<3), 30% were intermediate sands and only 11% were well-graded sands (Cu>5). The study also found that86% of the sites along the seasonal streams were dominated with medium sands while 10% were dominated with fine sands and the rest (4%) dominated by coarse and gravelly sands. From the results this study concludes that 59% of the 80 sites that were investigated in this study have a high potential for providing suitable sites for sand dams in Kitui South. Keywords: Sand Dams; Particle Size Distribution; Hydrology; Water Management; Kitui South, Keny

An Assessment of the Spatial and Temporal variations of Groundwater quality in Yatta Plateau in Kitui County, Kenya

The study is primarily focused on the assessment of groundwater quality in the Yatta Plateau of Kitui County. The study focused on the spatial temporal distribution of key chemical parameters namely pH, TDS, Colour, Total hardness, Turbidity, Conductivity, Total alkalinity, Fluoride and Iron. Groundwater samples were collected four times from the six target boreholes found on the plateau in the period between March 2015 and March 2016. The sampling programme covered two dry seasons and two wet seasons. Key physicochemical parameters were analysed using standard laboratory methods. The water samples were analyzed at the Water Resources Management Authority (WARMA) Water Quality Testing Laboratory in Nairobi. The results of the study show that there is no direct relationship between rainfall and variations of groundwater quality in the Yatta plateau. The influence of water abstraction on water quality was also limited. The dominant influence on groundwater quality in the Yatta Plateau was found to be the geological characteristics of the area. It was however found that there was spatial-temporal variability in different groundwater quality parameters that were analysed. The study recommends integrated groundwater resources management including continuous water quality monitoring in the Yatta Plateau in Eastern Kenya. Key Words: Groundwater quality, physic-chemical parameters, spatial-temporal variability, Yatta Plateau, Keny

The Impacts of Water Abstraction in Tropical Rivers: A Case of South West Upper Tana Basin, Kenya.

The study to determine the impacts of water abstraction in South West Upper Tana Basin which is part of the larger Upper Tana basin was undertaken in four major rivers, Thika, Kimakia, Kiama and Chania. Data for this study was obtained from the Kenya Meteorological department (KMD), Water Resources Management (WRA) and questionnaire surveys. The questionnaires were administered in the period between January 2018 and December 2018 to determine the impacts of water abstraction in both dry and wet seasons. Regression and correlation analysis was used to determine the nature and strength of relationships between different variables. The results of the study indicate that the main impacts of water abstraction are hydrological, environmental and socio-economic. The hydrological impacts include reduced water levels, changes in stream morphology, decreased turbidity and reduced siltation. Socio-economic impacts include increased income from crop production and conflicts while environmental impacts were mainly changes in riparian vegetation. The study established that the best combination of impacts of water abstraction in the South West Upper Tana Basin were changes in water turbidity, decline in water levels, improved crop yields, changes in channel morphology and siltation with a coefficient correlation r of 0.57 and coefficient of determination R2 of 0.52. To mitigate these impacts, there is a need for better enforcement of legislations on water abstraction and the monitoring of the river basins to curb water over-abstraction. Public awareness campaigns and involvement of stakeholders could also minimize these impacts. Keywords: Water abstraction, hydrological impacts, socio-economic impacts, environmental impacts, South West Upper Tana Basin (SWUT). DOI: 10.7176/JEES/9-5-08 Publication date:May 31st 201

A Comparative Study of the Physiochemical and Bacteriological Parameters of Potable Water from Different Sources in Kitui County, Kenya

Developing nations are experiencing an ever-increasing demand for safe water due to climate change and the ever-increasing human population. Various strategies including construction of shallow wells, boreholes and sand dams along the river are done to make water available to various households. However, availability of water sources near are faced with challenges of pollution from a variety of sources. The aim of this study was to determine the levels of selected bacteriological and physico-chemical parameters in three potable water sources namely Kiembeni borehole, Mwitasyano River and Kalundu Dam in Kitui County.  The quality of this water was compared to the standards for potable water prescribed by Kenya Bureau of Standards (KEBS). Representative sampling was conducted during the wet season (October 2019) and the dry season (August 2020) in the three sampling sites. The samples were analyzed for physico-chemical parameters: pH, color, turbidity, alkalinity, conductivity, iron, calcium, magnesium, hardness, chloride, fluoride, sulphates, ammonia, total dissolved solids and bacteriological parameters: total and fecal coliform. The analysis was performed at the Kenya Water Institute (KEWI) laboratory using standard procedures. The values obtained for the different water sources in the wet season and dry season were pooled and mean values calculated to determine the overall quality of drinking water. The results indicated that all the water sources had fecal coliform levels unsuitable for drinking water. Most of the values obtained for pH, color, alkalinity, conductivity, calcium, fluoride and sulphates in all sources of water were within the recommended potable water standards by KEBS. However, turbidity, iron and total coliform obtained values for borehole water samples were not within the recommended KEBS standards. The river and dam water samples were within the recommended standards for magnesium, hardness, chloride, ammonia and total dissolved solids. Although results indicate that some of the physico-chemical parameters were in conformance with the recommended standards, the overall bacteriological parameters render the water unsuitable for drinking.  Thus, public health intervention programmes should be focused on addressing various sources of water pollution including regular disinfection of water. Keywords: Water quality, Physico-chemical, Kitui County, Assessment DOI: 10.7176/JEES/12-11-05 Publication date: November 30th 202

To err is human, to correct is public health: a systematic review examining poor quality testing and misdiagnosis of HIV status.

INTRODUCTION: In accordance with global testing and treatment targets, many countries are seeking ways to reach the "90-90-90" goals, starting with diagnosing 90% of all people with HIV. Quality HIV testing services are needed to enable people with HIV to be diagnosed and linked to treatment as early as possible. It is essential that opportunities to reach people with undiagnosed HIV are not missed, diagnoses are correct and HIV-negative individuals are not inadvertently initiated on life-long treatment. We conducted this systematic review to assess the magnitude of misdiagnosis and to describe poor HIV testing practices using rapid diagnostic tests. METHODS: We systematically searched peer-reviewed articles, abstracts and grey literature published from 1 January 1990 to 19 April 2017. Studies were included if they used at least two rapid diagnostic tests and reported on HIV misdiagnosis, factors related to potential misdiagnosis or described quality issues and errors related to HIV testing. RESULTS: Sixty-four studies were included in this review. A small proportion of false positive (median 3.1%, interquartile range (IQR): 0.4-5.2%) and false negative (median: 0.4%, IQR: 0-3.9%) diagnoses were identified. Suboptimal testing strategies were the most common factor in studies reporting misdiagnoses, particularly false positive diagnoses due to using a "tiebreaker" test to resolve discrepant test results. A substantial proportion of false negative diagnoses were related to retesting among people on antiretroviral therapy. Conclusions HIV testing errors and poor practices, particularly those resulting in false positive or false negative diagnoses, do occur but are preventable. Efforts to accelerate HIV diagnosis and linkage to treatment should be complemented by efforts to improve the quality of HIV testing services and strengthen the quality management systems, particularly the use of validated testing algorithms and strategies, retesting people diagnosed with HIV before initiating treatment and providing clear messages to people with HIV on treatment on the risk of a "false negative" test result