Water Resources Authority Research Articles

FORECASTING OF FLOOD EVENTS FOR WATER RESOURCES MANAGEMENT IN GUCHA-MIGORI RIVER BASIN, KENYA

Floods are devastating natural disasters frequently occurring in many river basins such as Gucha-Migori River Basin, Kenya. However, non-structural countermeasures such as hydrologic modelling, flood proofing, and continuous forecasting have not been fully explored and implemented to reduce risk, damage, and vulnerabilities of flood events. The major challenge in flood forecasting is the selection of the relevant probability distribution. The main objective of the study was to forecast flood events in Gucha-Migori River Basin for integrated water resource management. Daily hydrological datasets between 1969 and 2015 were obtained from Water Resources Authority. After the ranking of independent flood events had been achieved, return periods and flood frequencies were computed. The relationship between flood magnitudes and their respective frequencies was through modelling using probability distribution functions (PDFs). The evaluated PDFs include Normal Distribution, Log-Normal Distribution, Gumbel Distribution, and Log-Person Type III Distribution. Coefficient of Determination (R2), Goodness of Fit test, and Best-Fit Distribution Curve guided selection of the suitable distribution model. The suitable probability distribution model out of the tested four was then applied to predict P-percent annual exceedance probabilities corresponding to specific flood magnitudes. From the results, out of the 132 flood events that occurred in the period 1969 to 2015, only 42 were identified as independent flood events. Based on the frequency analysis, the highest and lowest, and the average and standard deviation of the recorded independent flood events were 423.90, 240.8, 284.80 m3/s, and 45.54 respectively. It was revealed that the probability of a flood event of a magnitude equal to or exceeding the lowest (240.8 m3/s) and the highest (423.90 m3/s) occurring for a particular year were 0.98 and 0.02 respectively. Gumbel distribution curve was selected to be the best fit for the Gucha-Migori River Basin. According to the derived Gumbel's formula, the estimated magnitude for the return period 1.05, 1.11, 1.25, 2, 5, 10, 25, 50, 100, and 200 years were 221.38, 231.92, 245.77, 278.01, 321.39, 350.11, 386.39, 413.31, 440.03, and 466.65 m3/s. This research provides useful information for enhanced determination of probability occurrence of flood events and thus proper water resources planning and management strategies in the Gucha-Migori river basin.

Integrated Water Resource Management of Panjshir River Basin

In recent years, integrated water resource management has attracted the attention of policymakers and experts in the water sector. This method, which is very effective, faces many challenges in developing countries such as Afghanistan. The following research is based on the field method, which has been used for information from books, journals, and reliable scientific sites, and to collect basic information from a questionnaire that has been interviewed with 103 residents of Panjshir province, as well as from the analyzed data. The National Water Resources Authority has also been used. The findings of the research show that in the Panjshir river basin, only a foundation has been laid in the form of policies, strategies, and laws, but there are deficiencies in the fields of regular institutional framework and tools needed to perform tasks in this river basin. One of the departments of integrated water resource management has not been formed, and there are still few hydrological and hydro meteorological stations in this field. On the other hand, according to the respondents to the questionnaire, the role of women as a huge group of society in decision-making is also weak. Therefore, we conclude that the effectiveness of applying the principles of integrated water resource management in the Panjshir river basin is low due to the above reasons.

The Impact of Water Abstraction on River Mutonga Discharge Over the Last 30 Years

The declining water levels among rivers flowing through Tharaka Nithi County have been a major concern in the region for the last 30 years. The decline has adversely affected environmental sustainability, water resources, agriculture and the ecosystem. Understanding the relationship between rivers, change of climate and human activities are essential challenging areas. The research aimed to assess the impact of changed rainfall pattern and amount to the declining water levels in Mutonga River over years from 1990 to 2020 and it contribution to the changing water levels in river Mutonga. An exploratory survey and a correlational study were used to compile the data for this analysis. Three regional NEMA officials and three regional water resources authority officials were also surveyed, along with 270 residents in the River Mutonga area. The samples were based on 30% as per Mugenda Mugenda samples analysis. The rainfall and temperature data was acquired from the regional meteorological department based in Embu town. Data on river discharge was acquired from regional water resource authority (WRA) based in Meru town. The result may also recommend suitable practices for management of water resources and come up with disaster control measures in water sector. The local community may also benefit from the study by getting the right information on better methods of conserving water resources, the findings and recommendations from the study may be used as basis for future research related to this study. From the findings, results show that river Mutonga flows has been decreasing over the last 30 years, water abstraction trend has been rising over the entire period in three decades causing a tremendous decline in river discharge. climatic changes have been noted in the region with rainfall amount dropping significantly and temperatures increasing, this has led to decline of the river discharge due reduced rainwater adding to the rivers and increased evaporation rates which leads to loss of water from rivers to the atmosphere. The result from the research may be used to enlighten the County Government of Tharaka Nithi, in making decision, especially in development projects implementation and in the strategic plans of the County Government.

Distribution of Benefits and Risks in Inter-Basin Water Transfers: The Case Study of NCT I from Upper Tana Basin to Nairobi City

Inter-Basin Water Transfers (IBWTs) introduce complex socioeconomic, hydrological, ecological, and institutional impacts that are instrumental to decision-making. However, since most studies focus on the hydrological and ecological aspects of IBWTs for the development of sustainable water resources, it is necessary to investigate the distribution of risks (costs) and benefits of IBWTs among stakeholders. This study aimed to identify and categorize stakeholders, their relationships, and the distribution of risks/costs and benefits in the Northern Collector Tunnel phase I (NCT 1) IBWT using a stakeholder analysis method. The Athi Water Works Development Agency (AWWDA) and the Ministry of Water and Irrigation (MoWI) played a central role in the project. However, most stakeholders found the devolved units Water Services Providers (WSPs), Water Resources Authority (WRA), Water Resources Users Associations (WRUAs), and Murang'a County as the most critical institutions. Public participation in NCT1 was not inclusive but only done to meet the statutory project requirements. Significant risks of the project emerged, such as reduced river flows, drying of the springs, and Murang'a residents' ability to meet their water needs. Therefore, it is necessary to compensate for diverted water through a water levy to cover environmental externalities and catchment conservation. The increase in water supply for Nairobi City was perceived as the main benefit for the recipient basin, but an improved water levy with adequate cross-subsidies was pointed out as an instrument to catalyze water savings by the urban water utility.

Determination of the influence of socio-economic activities on streamflow in South West upper Tana basin, Kenya

The study aimed to determine the influence of socio-economic activities on streamflow undertaken in South West Upper Tana Basin, Kenya (SWUT), one of the larger Upper Tana Basin basins. In this study, primary data was obtained by administering questionnaires, while secondary data was obtained from Water Resources Authority (WRA). The administration of questionnaires was in the period between April 2019 and June 2020. Logit regression was run to determine the influence of the different socio-economic activities on streamflow. The results showed that agriculture was the main socio-economic activity influencing water abstraction in the study area. Agricultural practices such as farm size, income from crop sales and fertiliser use significantly influenced water abstraction with P values (0.04, 0.01 and 0.02) < 0.05. The study also established household characteristics such as the income of the household head, income level of household head, marital status, age, residence period, level of education, the technology used, and gender of the household head positively influenced water abstraction. However, these factors did not significantly influence water abstraction with P values of 0.23, 0.78, 0.50, 0.60, 0.74, and 0.52 for the income level of household head, marital status, age, residence period and level of education, respectively, being > 0.05. The study recommends the formulation of policies to ensure efficient water abstraction in the basin. Water Resources Authority should also ensure that all water abstractors are licensed to minimise over-abstraction.

Application of QUAL2kw and Forecasting models for assessment of pollutants in upper Athi River catchment in Kenya

Water pollution in the Athi river drainage basin, the fourth largest drainage basin in Kenya, has the potential of adversely impacting the aquatic biota and communities living downstream of the river. The upper part of the basin has experienced rapid industrialization in the recent past and there has also been increased encroachment of wetlands and forests for agriculture and settlement to cater for the increased population. The objective of this study was geared towards the generation of scenarios to predict future water quality trends in the upper parts of the Athi river basin. The prediction of the future water quality trends was undertaken in two phases: (i) the development of longitudinal water quality profile using QUAL2Kw model and (ii) prediction of the future water quality trends using the SPSS Forecasting tool. The collection of water quality data in established sampling stations located in the upper parts of the basin was carried out between January and December 2018. The archival data for the period 2015-2018 was obtained from Water Resources Authority (WRA) database for the determination of future trends in selected water quality parameters. The correlation analysis between the observed and predicted water quality parameters yielded strong R2 values for temperature-0.82, electrical conductivity-0.99, total dissolved solids-0.94, biochemical oxygen demand-0.66, chlorophyll a-0.89, total nitrogen-0.75 and total phosphorous-0.94. The standard error ranged between 0.01-0.42, indicating that the model is reliable for predicting water quality parameters in the river. The available archival monthly data from 2015 to 2018 were averaged for time series forecasting to generate future water quality scenarios of the river for the period 2019-2030. The results showed that dissolved oxygen exhibit a decreasing trend in future indicating depletion of oxygen in water. There will also be significant increasing trends for Electrical Conductivity, Total Suspended Solids, Biochemical Oxygen Demand and Iron in future. There is a risk that the pollutants will increase to unsafe levels in the Athi River if appropriate management actions are not taken by the concerned agencies

Assessment of hydrological water balance in Lower Nzoia Sub-catchment using SWAT-model: towards improved water governace in Kenya

Kenya's catchments has both natural and disturbed environments. Within these environments, there has been interaction between hydrological, physical and ecological characteristics. Therefore, impacts of Land Use Land Cover (LULC) change on surface and sub – surface hydrology needs to be well understood due to the increasing population competing for scarce natural resources such as water, trees and forest land. The water balance components' spatial and temporal dynamics in relationship to the LULC change between 2003 and 2018 in the Lower Nzoia Sub – Catchment (LNSC) in Kenya was therefore assessed. Landsat data with 30 m (m) spatial resolution was used in understanding LULC dynamics of the study area using Supervised Classification Approach (Interactive Classification Method) in ArcGIS 10.5. After landsat image classification, key water balance components including; surface runoff (SURFQ), lateral flow (LATQ), groundwater recharge (BASEQ), deep acquifer recharge (DEEPQ), evapotranspiration (ET) and groundwater revap (REVAP) for years 2003 and 2018 were estimated using SWAT model in ArcSWAT. The overall accuracies for 2003 and 2018 classified images were 75.9% and 98.9% respectively which are showing good values. The results of the study showed that agricultural land coverage reduced from 83.1% in 2003 to 78.6% in 2018. Rangeland on the hand increased from 6.3% to 9.8% while urban/built – up area increasing from 10.6% to 11.6%. The annual water balance components from the LULC distribution of the two time periods shows that ET reduced, SURFQ increased, BASEQ reduced, DEEPQ reduced, LATQ reduced and REVAP reduced. At catchment level, results show that 2018 had a higher water balance than 2003 which can partly be explained by land cover decrease. The relationship between rainfall distribution, Land Surface Temperature (LST) and LULC change were further compared. At the same time, the study found out that there is limited focus to date on rural communities climate adaptive capacity. Hence, water institutions in the sub – catchment such as Water Resources Authority (WRA) are yet to fully mainstream adaptive capacity into their organizational structure and policies.

EVALUATION OF SPATIAL AND TEMPORAL HYDROLOGICAL DROUGHT USING SURFACE WATER SUPPLY INDEX IN MALEWA RIVER CATCHMENT, NAIVASHA

There has been a critical problem of the devastating natural hazard (hydrological drought) which greatly affects a significant proportion of the large population particularly those living in arid and semi-arid areas. The flow regime of the Malewa River is reducing due to the river fluctuation, increasing scarcity of water during dry periods. The purpose of this research was to assess spatial and temporal hydrological drought using Surface Water Supply Index (SWSI) at Malewa River catchment. The data were based on hydro-meteorological data which included rainfall, level of water at Lake Naivasha, and streamflow of Malewa River for the years 1980-2018. They were obtained from Water Resources Authority (WRA) in Naivasha and Kenya Meteorological Department (KMD) in Nairobi, Kenya. The field data were first normalized to have all input attributes temporary variables with their distribution having zero means and a standard deviation of 1. Later the normalized data were calculated using basin-calibrated algorithm of SWSI to determine the hydrological condition. In SWSI, the highest percentage of classification for the stations were near the average of -0.9 to 1.0, with 34% for the Malewa area and 30% for the Turasha area. In spatial distribution analyses, hydrological drought severity was highest along the southern part of the catchment and lowest along with Eastern and North-Eastern areas. Therefore, hydrological drought severity was experienced in the catchment in terms of temporal and spatial analyses and increased along the flow path of the river. Hydrological drought assessment shows a technical manner for a comprehensive understanding of drought offering proper mitigation strategies and plan to control this natural disaster.

English

Hydropower is cost effective environment friendly and worldwide proven sustainable energy source. Driven by streamflow stream flows, it is vulnerable to climate change and land use change. The hydropower production from the two-existing run-of-river hydropower projects on the Sondu Miriu River are vulnerable to rainfall variability and requires proper understanding of the climate change trends and policies to support sustainable hydropower development and put in place strategies for building resilience for the local communities. The objective of this paper is to examine climate change trends and their impacts on hydropower in the Sondu Miriu River basin. The methodology involved analysis of downscaled climate data from CORDEX for the period from 1950 to 2100, gridded data from Kenya Meteorological department for a period of 2007 to 2018, river flows data from Water Resources Authority for a period of 2007 to 2018 and hydropower output data from KenGen for a period of 2007 to 2018 to examine the climate change trends within the Sondu Miriu River basin and impacts on hydrology and hydropower. The results indicate that maximum and minimum annual temperature increased by 0.7 and 0.9°C, respectively between 1950 and 2005. Both the maximum and minimum annual temperatures are projected to increase by 1.9°C based on the RCP4.5 and RCP8.5 scenarios between 2006 and 2100 within the Sondu Miriu basin. Annual rainfall increased by 74.8 mm between 1950 and 2005. This is projected to increase by 24.7 and 117.8 mm based on RCP4.5 and RCP8.5 scenarios, respectively. For the period between 2007 and 2018, the observed maximum increased by 5°C while the minimum temperatures decreased by 1°C. The rainfall decreased by 193.14 mm while the mean daily river flows decreased by 0.3 m3/s annually during the same period. This resulted in the decrease of hydropower production by 8.3 GWh in Sondu Miriu HPP between 2007 and 2018 while the production reduced by 14.18 GWh for Sang’oro HPP between 2012 and 2018. Understanding climate change trends within Sondu Miriu River basin should guide the planning for hydropower development projects.   Key words: Climate change, hydropower, Sondu Miriu River basin, downscaling, impacts.

Settlement Schemes and their Implication on Eastern Mau Water Catchment, Kenya

Settlement schemes are aimed at settling landless people and those displaced by disasters to support socio-economic and environmental development of a country. Eastern Mau Forest Reserve is an important water catchment that has settlement schemes established, which has led to encroachments and degradation of the catchment. This paper, therefore, assesses the implications of human settlements on Eastern Mau water catchment by examining the trends in land use/cover change and river flows for four decades. Primary data was collected from key informant interviews based on purposive sampling whereas secondary data was derived from Landsat satellite images over a 10-year period and analysed using Maximum Likelihood Function from ArcGIS. Data on river flows from River Njoro was obtained from Water Resources Authority Office in Nakuru. Rainfall and temperature data were obtained from Kenya Meteorological Station in Nakuru. Time series analysis is used to understand the trend in river flows over time while Pearson correlation is used to determine relationship between farmlands and river flows. The results indicate a sharp decline in forest cover by 42.7% and an increase in farmlands by 41%. Dense vegetation and farmlands have an inverse relationship as an increase in farmlands lead to a decrease in forest cover. People have settled beyond the established settlement schemes boundaries leading to encroachment and drying up of some rivers. There is also an increase in rainfall and river flows over the years, with monthly river flows increasing in peak flows and declining during low seasons. There is a positive correlation between farmlands and river flows between 1989 and 2020. There is need for regeneration of encroached areas and defining boundary of Eastern Mau to allow initiatives and interventions that help with sustainable management of the catchment area.

Characterization and monetization of Mount Marsabit ecosystem watershed services, Marsabit County, Kenya

The study aimed at addressing Mount Marsabit ecosystem watershed service valuation information gap by: - a) analyzing the typology and mapping the spatial distribution of water supply points within the forest ecosystem, b) documenting types of water consumers and service beneficiaries and, c) undertaking monetary value estimation of the ecosystem watershed services in terms of the water supply market. The mapping of ecosystem water points involved a physical inventory of three target wards in Marsabit Sub-County, namely Marsabit Central, Sagante/Jaldesa, and Karare and recording of GPS locations and thereafter overlying the water sites on a map of the area using ArcGIS. The analysis of water consumers and valuation of the ecosystem watershed service was undertaken through the market price method (MPM) using existing secondary and primary data from relevant offices and from face-to-face interviews of 275 respondents. The findings showed that Marsabit forest ecosystem was supporting a total of 115 active water points which were dominated by shallow wells (68) followed by boreholes (21), water pans (14), springs (4), streams (6), and crater lakes (2). The overall pattern showed boreholes as the principal water access types (47.3%), followed by shallow wells (15.3%), springs (12%), water pans (8.7%), streams (2%), and crater lakes (0.7%). The mountain ecosystem was found to be more hydrologically active on the eastern windward side within the 1300-1300m elevation belt. The overall value of the Mount Marsabit ecosystem watershed service was estimated at Ksh 58,285,026 ($582,035) per year. It is recommended that the Water Resources Authority (WRA), the Kenya Water Towers Agency (KWTA), and the County Government of Marsabit should collaborate with local communities and the local water vendors to initiate a payment for ecosystems services (PES) that will plough back some of the revenue generated from the water market towards conservation of Mount Marsabit Forest ecosystem.

Age-dependent association between SARS-CoV-2 cases reported by passive surveillance and viral load in wastewater

The actual number of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is difficult to estimate using a case-reporting system (i.e., passive surveillance) alone because of asymptomatic infection. While wastewater-based epidemiology has been implemented as an alternative/additional monitoring tool to reduce reporting bias, the relationship between passive and wastewater surveillance data has not yet been explicitly examined. As there is strong age dependency in the symptomatic ratio of SARS-CoV-2 infections, here, we aimed to estimate i) an age-dependent association between the number of reported cases and viral load in wastewater and ii) the time lag between these time series. The viral load in wastewater was modeled as a combination of contributions from virus shedding by different age groups, incorporating the delay, and fitted with daily case count data collected from the Massachusetts Department of Public Health and SARS-CoV-2 RNA concentration in wastewater recorded by the Massachusetts Water Resources Authority. The estimated lag between the time series of viral loads in wastewater and of reported cases was 10.8 (95% confidence interval: 10.2–11.6) and 8.8 (8.4–9.1) days for the northern and southern areas of the wastewater treatment plant, respectively. The estimated contribution rate of a reported case to the viral load in wastewater in the 0–19 yr age group was 0.38 (0.35–0.41) and 0.40 (0.37–0.43) for the northern and southern areas, and that in the 80+ yr age group was 0.67 (0.65–0.69) and 0.51 (0.49–0.52) for the northern and southern areas, respectively. The estimated lag between these time series suggested the predictability of reported cases 10 days later using viral loads in wastewater. The contribution of a reported case in passive surveillance to the viral load in wastewater differed by age, suggesting a large variation in viral shedding kinetics among age groups.

Modeling Water Supply and Demand for Effective Water Management in the Sana’a Basin in Yemen

Modelling system is the core for the evaluation of water related sectors in the Sana’a Basin. The numerical modelling (MODFLOW) has emerged as an effective tool for managing groundwater resources and predicting future responses, especially when dealing with complex aquifers systems and heterogeneous formations. MODFLOW model has been used herein as a management tool for the targeted sub- basins in Sana’a Basin such (Wadi Bani Hawat, Wadi Dhahr & Al-Ghayl, Wadi Hamdan & As Sabrahand Wadi Ghayman); the most important groundwater resources for domestic and agricultural sectors in Sana’a basin. A conceptual model was designed according to the actual groundwater dynamic flow system in the 2010 Hydrosult Sana’a Basin Model. Also, the governing partial parabolic differential equation was defined, including the vertical conductivity flow between the aquifers. Total groundwater abstraction values from previous studies were compiled, including the 2015 well inventory data of National Water Resources Authority –Sana’a Basin.In this study, three simulations of groundwater development scenarios were distinguished. The first scenario is applied for evaluation of the present status and till 2025. The second and thethird scenarios are focused on the effect of water augmentation i.e. decrease the present rate of groundwater abstraction to 30% and 50% respectively, with considering the highly intervention of IWRM structure of Sana’a basin on the on-going activities related to change land use, change crop pattern, value chain, marketing, modern irrigation techniques, water harvesting techniques, treated waste reuse etc…. Also other Modules were used in calculating the groundwater demand, deficit and unemployment in agricultural sector inSana’a Basin. Scenario 3 gives a remarkable improvement of the water resources system in the four sub-basins within a reasonable period (in the year 2025), thus, it will keep the water resources sustainability; but the unemployment in agricultural sector in Sana’a Basin in scenario 3 will be is the highest value if comparing with the other two scenarios. It will reachin 2025 under scenario 2 and scenario 3 to 10432 and 14762 respectively while in scenario 1 the unemployment will disappeared in 2025. This study is recommended that irrigation systems should be improved, usage of harvesting water methods and treated waste water reuse for agriculture to avoid the depletion of Sana’ Basin aquifer and to reduce unemployment in agricultural sector in Sana’a Basin.
 Keywords: Groundwater Flow Model, MODFLOW, Management Scenarios, Sana’a Basin, Targeted Sub-Basins.

Modeling Water Supply and Demand for Effective Water Management in the Sana’a Basin in Yemen

Modelling system is the core for the evaluation of water related sectors in the Sana’a Basin. The numerical modelling (MODFLOW) has emerged as an effective tool for managing groundwater resources and predicting future responses, especially when dealing with complex aquifers systems and heterogeneous formations. MODFLOW model has been used herein as a management tool for the targeted sub- basins in Sana’a Basin such (Wadi Bani Hawat, Wadi Dhahr & Al-Ghayl, Wadi Hamdan & As Sabrahand Wadi Ghayman); the most important groundwater resources for domestic and agricultural sectors in Sana’a basin. A conceptual model was designed according to the actual groundwater dynamic flow system in the 2010 Hydrosult Sana’a Basin Model. Also, the governing partial parabolic differential equation was defined, including the vertical conductivity flow between the aquifers. Total groundwater abstraction values from previous studies were compiled, including the 2015 well inventory data of National Water Resources Authority –Sana’a Basin.In this study, three simulations of groundwater development scenarios were distinguished. The first scenario is applied for evaluation of the present status and till 2025. The second and thethird scenarios are focused on the effect of water augmentation i.e. decrease the present rate of groundwater abstraction to 30% and 50% respectively, with considering the highly intervention of IWRM structure of Sana’a basin on the on-going activities related to change land use, change crop pattern, value chain, marketing, modern irrigation techniques, water harvesting techniques, treated waste reuse etc…. Also other Modules were used in calculating the groundwater demand, deficit and unemployment in agricultural sector inSana’a Basin. Scenario 3 gives a remarkable improvement of the water resources system in the four sub-basins within a reasonable period (in the year 2025), thus, it will keep the water resources sustainability; but the unemployment in agricultural sector in Sana’a Basin in scenario 3 will be is the highest value if comparing with the other two scenarios. It will reachin 2025 under scenario 2 and scenario 3 to 10432 and 14762 respectively while in scenario 1 the unemployment will disappeared in 2025. This study is recommended that irrigation systems should be improved, usage of harvesting water methods and treated waste water reuse for agriculture to avoid the depletion of Sana’ Basin aquifer and to reduce unemployment in agricultural sector in Sana’a Basin.
 Keywords: Groundwater Flow Model, MODFLOW, Management Scenarios, Sana’a Basin, Targeted Sub-Basins.

Assessment of Ground water Quality in Mumbuni Estate, Machakos Town, Kenya

The rapid increase of global human population has led to more people living in towns and cities in the recent past. This has brought pressure on water service provision and sanitation infrastructure in many cities and towns including Machakos town. Due to surface water shortages, groundwater has been an alternative. This includes sinking of boreholes and hand dug shall wells. This study evaluated the concentration levels of physical and chemical parameters of water in selected boreholes and shallow wells in Mumbuni estate, Machakos town. A total of three boreholes and three shallow wells were included in the study. Water samples were collected in triplicates after every two weeks for a period of one and a half months from the selected sampling sites. The samples were transported to the Water Resources Authority (WRA) central laboratory in Nairobi for analysis using the standard methods for the examination of ground water. Independent T-test was used to analyze data and significance levels accepted at p≤0.05. The results obtained were compared with both the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) drinking water standards in order to determine the quality of ground water and its suitability for drinking. All the parameters measured varied significantly between borehole water and shallow well water except for Calcium, Magnesium and potassium (p≥0.05). pH, turbidity, electrical conductivity, Chloride, Fluoride and Sulphates were within the WHO and KEBS recommended limits for drinking water. Other parameters tested such as Calcium, Magnesium and Potassium were also within acceptable limits. The study concluded that water from boreholes and shallow wells in Mumbuni estate is suitable for drinking.

Assessment of Water Quality in Kalundu Stream and Kalundu dam in Kitui County, Kenya

This study aimed to assess levels of selected physico-chemical and bacteriological loads of Kalundu stream and Kalundu dam. Sampling was conducted from February to April 2019 in three selected sampling sites. Surface water samples were collected and analyzed for fifteen physico-chemical parameters. Water temperature, pH, turbidity and electrical conductivity were measured on site. Biological oxygen demand (BOD), Chemical Oxygen Demand (COD), total hardness and alkalinity, selected major anions and cations were analyzed at a Water Resources Authority laboratory using standard procedures. Data analysis was carried out using one-way analysis of variance and significant differences accepted at p≤0.05. Results showed that pH, fluoride, sulphates, total hardness and alkalinity were within WHO set standards for drinking water. However, turbidity, EC, Fe, Ca, Mg, Nitrites and Chlorides were above the WHO recommended levels for drinking water. Both total coliforms and E. coli were exceedingly high and ranged from 385±188.9 to 337,133±124,970 MPN/100ml and 70.70±46.50 to 3941183±2771080 MPN/100ml respectively. The findings revealed that water quality of Kalundu stream and Kalundu dam is highly polluted with pathogenic microorganisms and a potential risk to human health. Therefore, measures to curb microbial pollution should be taken by the relevant municipality authorities of Kitui County government. Keywords : Assessment, Water quality, Bacteriology, Kalundu dam, Kitui County DOI: 10.7176/JEES/11-1-05 Publication date: January 31 st 2021

English

Water samples for physico-chemical, heavy metals and bacteriological analyses were collected from 4 selected points along Mitheu Stream flowing through Machakos Municipality once every month from June 2019 to September 2019. The samples were analyzed in Kenya Plant and Health Inspectorate Service and Water Resources Authority laboratories then data subjected to one-way analysis of variance to test significant differences (P≤0.05). The results were compared with World Health Organization guidelines to assess the suitability of the water for irrigation use. Results showed that the levels of the Biological Oxygen Demand and the Chemical Oxygen Demand in Mitheu Stream were higher than critical values permitted by the World Health Organization for irrigation water. Nitrates and Sulphates were within critical limits; however, Phosphates were higher than permissible limits at all the sampling points. Heavy metals concentrations for Cu, Pb, Zn and Cr were within allowable limits for irrigation water, but Cd was above the limit. Both total coliforms and Escherichia coli counts exceeded allowable limits for irrigation water. As such, Mitheu Stream can be considered polluted and the water unfit for irrigation farming. The Municipal authorities, working with other relevant stakeholders should take appropriate measures to mitigate stream pollution from untreated effluent discharged into the stream.   Key words: Physico-chemical, heavy metals, total coliforms, effluent.

Using Extreme Value Theory to Estimate Available Water in the Upper Awach-Kibuon Catchment in Nyamira County, Kenya

In the management of water resources projects, water managers are often interested in quantifying the frequency and magnitude of floods that will occur at the management areas or units. The frequency analysis of these events is one of the most important aspects that define the relationship between the magnitude and the frequency of an event, for which that event is exceeded. Frequency analysis therefore find its usefulness in the design and implementation of water projects such as in irrigation water requirement where the interest is on how much water can be available from a water resource to support irrigation throughout the year. The objective of this paper therefore was to assess the available water, using the extreme value analyses methods, that can be put to other uses such as irrigation water demand, domestic water requirement after due consideration to the environmental flow. The available water was estimated by deducting the following from the 80% probable flows orQ80: i) Deduction of estimated existing/future abstractions- determined from available information on irrigation activities along the three rivers (upstream and downstream) and ii) Deduction of the environmental flow - taken as 30% of the Q95 probable flow based on monthly mean flows. In particular this research was biased towards supporting the water requirement for a proposed irrigation project in the study area. The area of study was Awach-Kibuon catchment of the Lake Victoria South Catchment Area. This river catchment drains parts of Nyamira County through the Awach-Kasipul sub-catchent (Nyabomite, Charachani and Eaka tributaries). Data used included daily rainfall and temperature data obtained from the Kenya Meteorological Department Headquarters in Nairobi while daily discharge or flow levels data from the three tributaries i.e. Nyabomite, Charachani and Eaka were obtained from the Water Resources Authority (Kisii sub-regional office). The flow levels from Nyabomite, Charachani and Eaka were converted to river discharge using appropriate rating curves. Rainfall data was used with the Curve Number method to estimate river discharge at Eaka where flow levels were hardly available. Flood frequency distributions (GEV, the Gumbel) with different methods of parameter estimations (moments, maximum likelihood, probability weighted moments) were then used to estimate flow magnitudes corresponding to specific return periods (Q50, Q80 and Q95) and generate flow duration curves. Results from the flood frequency analysis from the General Extreme Value and Extreme Value type 1 distribution using the methods of moments (mom), maximum likelihood (ML) and Probability Weighted Moments (PWM) indicated the best distribution to be EV1-PWM since it exibited the lowest standard error estimates. Based on the most suitable distribution (EV1-PWM), the probabilities of exceedance were computed and used to estimate the water available for irrigation purposes at the three target gauging stations in the sub-catchment.From the results, a larger volume of water is available for irrigation at Charachani, for example, lowest being 0.388 cumecs in the month of July compared to 0.147 cumecs for Nyabomite and 0.249 cumecs for Eaka.. The largest amount of water for irrigation is available during the months of May and November, with peaks corresponding to those of the rainy seasons. The months with the least available water for irrigation are December, January and February, which also corresponds with the dry seasons. These results were used to inform planning in setting up of flow control structures for irrigation project in the Charachani-Eaka-Nyabomite cluster in Nyamira County.

Comprehensive integrated index-based geochemistry and hydrochemical analyses of groundwater resources for multiple consumptions under coastal conditions.

The primary objective of this study was to assess the quality of groundwater in the Guilan aquifer, a principal aquifer in the north of Iran, for drinking, irrigation, and industrial purposes. In this regard, groundwater samples have taken from a database provided by the Water Resources Authority of Guilan Province, Iran's Ministry of Energy. The studied four main regions of this aquifer were Talesh, Astaneh, Lahijan, and Foomenat. Achieved results were compared with the maximum permissible limit values recommended by the World Health Organization (WHO) and Food and Agriculture Organization (FAO) water standards for drinking and agricultural purposes, respectively. Moreover, evaluation of water suitability for industrial application was determined. According to the different indices, groundwater quality is suitable for irrigation purposes in all studied areas. A Piper diagram illustrated that the most dominant water type was Ca-HCO3 in the all studied areas. This result also is consistent with results from the analysis of mineral saturation index. Accordingly, the result of water quality index (WQI) revealed that the groundwater in the Guilan aquifer could categorize from excellent to poor quality classes. However, the majority of water samples in Astaneh region mostly fall into the poor water class. The calculation of corrosiveness and scaling indices as Ryznar stability index (RSI) illustrated that a large number of the samples could be classified into aggressive and very aggressive categories. The results additionally showed that tendency to form scale based on Puckorius scaling index (PSI) was observed in some groundwater samples. Overall, the status of groundwater quality in Talesh region was noteworthy better than the other studied regions, while Astaneh region is more vulnerable with elevated contents of ions and physicochemical parameters.

Evidence of groundwater vulnerability to climate variability and economic growth in coastal Kenya

Climate change and future abstraction regimes will influence the availability of groundwater resources. To alleviate any potential negative effects on aquifer systems and dependent industrial and human uses, it is important to develop long-term water management plans. This study evaluates the effect of climate change and future increased groundwater demand from a coastal aquifer located in Kwale County in southern Kenya. A previously calibrated numerical groundwater flow model has been used as an assessment tool to study how future climate (precipitation and temperature variation) and groundwater abstraction changes will affect the aquifer system. The groundwater flow model was built to simulate the period 2010 to 2017, and eight future model scenarios were developed that cover six hypothetical future years. Future groundwater abstraction has been based on current allocations and future estimates made by Kenya’s Water Resources Authority. Future rainfall scenarios have been constructed based on a long historical data series (from 1959 to 2017) and the Standard Precipitation Index. The main results show that future abstraction increases due to economic growth exerts a minimum impact compared with expected climate variability. Recharge depends on intense rain events with important implications for both dry periods and for an average rainfall year. A succession of extended dry seasons may affect all water users. However, the groundwater level decline in the local shallow aquifer can reach five meters, with important consequences for local community water supplies. The most significant groundwater decline in drought periods is observed in the area surrounding the pumping wellfields in the deep aquifers, where the effects of drought and significant abstraction are multiplied. However, the effect of increased abstraction on the shallow aquifer system is limited. Despite groundwater level decline observed during prolonged dry periods, a dry period followed by a humid period leads to the relatively swift recovery of the groundwater system.