by Opere A.O. and A.K. Njogu
Original Research
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.
American Journal of Water Resources. 2020, 8(4), 200-210. DOI: 10.12691/ajwr-8-4-6
Pub. Date: September 02, 2020
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by Djim M. L Diongue, Niokhor Ndour, Mouhamadou D. Fall, Diakher H. Madioune, Babacar Dieng and Serigne Faye
Original Research
Hydrogeological and hydrochemical investigations were used to develop a conceptual model of the Continental Terminal (CT) aquifer functioning in the Oussouye plateau (South Senegal). Two field campaigns were carried out in June and October 2017 to measure physicochemical parameters and groundwater sampling. The geometry of the CT was established using geophysical technics (electrical methods) and the drilling logs from previous studies carried out in Oussouye region. These investigations led to build the mathematical model under the Visual modflow interface with the Modflow-2000 code developed by USGS. The results show a general trend of groundwater flow towards the Casamance River and its tributaries from piezometric mounds in the central area of the plateau which represent the potential recharge zones. Regarding chemical quality, electrical conductivity varies from 28 to 1314 µs/cm with high variance and standard deviation values reflecting variable sources, geochemical and dilution processes occurring in the plateau. The analysis of water samples shows an excellent groundwater quality. Major ions contents do not exceed WHO standards except Iron (Fe) which are relatively high in some wells. The mathematical model was calibrated in steady state. The average difference between simulated and observed head is 0.009 m and the root mean squared is less than 0.2m. Simulations under transient conditions showed that the groundwater is vulnerable to high pumping rate due to the drawdowns at the catchment wells, which can reach 7 m for 300 m3/d. This significant drawdown should be avoided for this type of piezometric configuration where the maximum hydraulic head is around 5 m. However, the model revealed a sustainable groundwater potential for the needs of local and neighboring populations by 200m3/d.
American Journal of Water Resources. 2020, 8(4), 191-199. DOI: 10.12691/ajwr-8-4-5
Pub. Date: September 01, 2020
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by Adama Gassama Jallow, Djim M. L Diongue, Huguette C. Emvoutou, Daouda Mama and Serigne Faye
Original Research
Remote sensing (RS) and Geographic Information System (GIS) play a crucial role in understanding groundwater potential recharge in semi-arid areas. In this present study, groundwater recharge zone map is delineated for the shallow aquifer in the Greater Banjul Area (GBA) using GIS, RS and Multi-Criteria Evaluation (MCE) technique utilizing seven criteria (geology, land-use/cover, slope, drainage density, soil texture, groundwater fluctuation and aquifer transmissivity). Analytical Hierarchical Process (AHP) is used as MCE technique to normalize the weights of the various criterion. Each class of the different themes was assigned suitable score and normalized using a Fuzzy membership algorithm. Thematic layers were integrated using Weighted Linear Combination (WLC) in a GIS platform to generate groundwater recharge zone maps. The recharge map thus obtained was divided into four classes (poor, moderate, good, and very good) based on their influence to groundwater recharge. Results indicates that about 10.5 % of the total study area falls under ‘poor’ and ‘moderate’ zone and cover the estuarian portion of GBA, 40% of the total area falls under ‘very good’ zone which is a good indication for future artificial recharge planning and potential drilling of boreholes.
American Journal of Water Resources. 2020, 8(4), 182-190. DOI: 10.12691/ajwr-8-4-4
Pub. Date: September 01, 2020
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by Jilani C. Chiro, Romulus Abila and Aggrey Thuo
Original Research
The world famous Masai Mara Game Reserve is experiencing an unprecedented expansion in tourist facilities to accommodate increasing traffic in this water scarce environment. A major direct environmental impact of this expansion is wastewater released to the fragile environment from these facilities. The objective of this study is to examine the effects of wastewater management methods on quality of wastewater in 4 purposively selected high-end tourist facilities located in Sekenani within Masai Mara Game Reserve by assessing seasonal quality of effluent discharged. Water samples were collected randomly from the effluent of the facility during both wet and dry seasons and were subjected to analysis for: pH, Temperature, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Phosphates, Nitrates, Electrical Conductivity (E.C), Dissolved Oxygen (DO), Turbidity, Total Suspended Solids (TSS) and Coliforms. Data were analysed using SPSS software and tested using analysis of Variance at 0.05 confidence level. Quality of wastewater was generally poor and dissolved oxygen, TSS, and coliforms showed variation between the wet and dry seasons. Single septic tank and septic tank and soak away treatment approaches produce water with the lowest quality based on Water Quality Index (WQI). This poses a great threat to not only the health of the communities relying on the recipient rivers as sources of water but also the Masai Mara ecosystem. To mitigate against discharge of poor quality wastewater to the environment, we recommend incorporation of modern innovative environmentally sustainable wastewater management technologies e.g. constructed wetlands to water treatment systems and robust enforcement of national environmental regulations. Further studies should include monitoring changes in macroinvertebrate species diversity and abundance along the recipient streams to provide a more holistic and integrated assessment of the ecological impact of the wastewater on the receiving lotic environments.
American Journal of Water Resources. 2020, 8(4), 173-181. DOI: 10.12691/ajwr-8-4-3
Pub. Date: August 19, 2020
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by OKOYA A. A. and ELUFOWOJU M. A.
Original Research
This study assessed the physico-chemical quality parameters of ground water bodies around the industry, with a view to evaluating the impact of the water bodies for the industry, and by extension the health of people of neighbouring communities who depend on these groundwater bodies for their water needs for domestic and other purposes. Water samples were collected from five ground water bodies. Physico-chemical analysis was carried out on the samples using standard methods. The highest and least values of turbidity (44.47 ± 34.37 and 7.99 ± 1.89 NTU) were recorded in the well and borehole during the wet season respectively. Highest value of pH (6.65 ± 0.13) was recorded in the well during the dry season, while the least value (5.94 ± 0.15) was found in borehole water sample during the wet season. TDS was highest (113.23 ± 14.76 mg/L) in the well during the dry season, while it was least (71.69 ± 17.68 mg/L) in the borehole during the wet season. Least value of DO (4.20 ± 0.71 mg/L) and the highest value (6.00 ± 0.42 mg/L) were recorded during the dry season, in borehole and well respectively. Ca2+and Cl- were highest in the well during the wet season (26.31 ± 5.64 and 16.08 ± 2.28) mg/L respectively but their least values 16.37 ± 3.67 and 8.91 ± 1.46 respectively occurred in the borehole during the dry season. Highest values of Cd (0.093 ± 0.0043 mg/L), Fe (0.69 ± 0.05 mg/L) and Pb (0.24 ± 0.03 mg/L) were recorded in the borehole during the dry season, but the least value of Cd (0.086 ± 0.0028 mg/L) was found in the well during the dry season, while least values for Fe and Pb (0.27 ± 0.036 and 0.012 ± 0.0086) mg/L respectively were found in the well during the wet season. The study concluded that values of turbidity, dissolved oxygen, cadmium, lead and iron significantly exceeded the national (NSDWQ) and international (WHO) permissible limits. The high values of these parameters, especially turbidity and heavy metals, may make the water toxic, and pose serious health challenges to people who drink the water.
American Journal of Water Resources. 2020, 8(4), 164-172. DOI: 10.12691/ajwr-8-4-2
Pub. Date: July 28, 2020
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by Ibrahim Habib Adamu, Abdulkarim Mubarak, Grema Haruna Muhammed, Abdullahi Ibrahim Mohammed and Hamidu Hassan
Original Research
Water quality of shallow floodplain aquifers in the Gidan Gulbi Fadama area of Gada, Sokoto State, Nigeria was assessed using water quality pollution indices for both irrigation and domestic use. Drinking water quality was assessed using pollution indices including concentration factor (CF), contamination degree (CD) and heavy metal pollution index (HPI), while irrigation water quality parameters such as sodium adsorption ratio (SAR), magnesium adsorption ratio (MAR), soluble sodium percentage (SSP), Kelly ratio (KR), residual sodium carbonate (RSC), permeability index (PI) and total hardness (TH) were used to evaluate the suitability of the water for irrigation purposes. Five heavy metals (Fe, Zn, Mn, Cr, and Cd) were selected to be assessed alongside other inorganic elements. The CF shows low intensities of contamination for Mn, Cr, and Zn while Fe and Cd have high and very high contamination intensities respectively. The results of CD and HPI indicate moderate to high contamination in the study area. The Fe most likely originates from the surrounding rocks of Taloka Formation, during fluid-rock interaction while the high degree of Cd contamination suggests an anthropogenic source. Given the land use pattern in the study area, the most likely source of the anthropogenic Cd is from pesticides, herbicides and fertilizers utilized for agricultural purposes. The areas with highest intensity of contamination (GW2, GW4 and GW7) are within or proximal to farmlands, consistent with the earlier inferred anthropogenic (agriculture) source for the major heavy metal pollutant (Cd). Furthermore, all of the water in the study area falls within the Ca-Mg/HCO3 type as revealed by the piper diagram and Schoeller plots, moreover, except for the total hardness (with a mean level of 253.13 mg/l), all other irrigation quality parameters suggest that the water is suitable for irrigation.
American Journal of Water Resources. 2020, 8(4), 155-163. DOI: 10.12691/ajwr-8-4-1
Pub. Date: July 23, 2020
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