Intergrated Water Resources Management

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Generalized characteristics of intense rainfall and peak discharges in Athi basin, Kenya
(JSHWR Committee on Editorial and Publication Affairs, 1995) Nyadawa, Maurice O.; Kobatake, Shigeki; Ezaki, Kazihiro
Presented in this paper is a study clarifying any distinctions or similarities in trends of extreme value statistics of rainfall and discharges recorded at stations sampled all over a basin traversing three distinct climatic zones in Kenya. It is found that in Athi basin, difference in seasonal rainfall pattern affect general characteristics of intense rainfall more significantly than spatial variation of mean annual rainfall. Survey of flood potential of the basin revealed zones which are considered hydrologically homogeneous and heterogeneous cases.
Estimating Transmission Losses in the Main Channel of River Tana, Kenya
(J-Stage, 1997) Nyadawa, Maurice O.; Kobatake, Shigeki; Ezaki, Kazuhiro
This study has presented correlation equations thought to define channel loss in River Tana in Kenya. Modified Tank Model is used to transfer runoff information from gaged basins to ungaged ones in the study area. The study has revealed that channel loss has two step functions corresponding to flow rates below 800m3/s and larger values.
Importance of Indeginous Macrophytes in Control of Water Hyacinth in the Nyanza Gulf of Lake Victoria, Kenya.
(Aquadocs, 2000) Omondi, Reuben; Gichuki, John
Observation of macrophytes dynamics in the Nyanza gulf of Lake Victoria is ongoing since the early 1990s. A checklist of the macrophytes and their distribution in the study area is provided. Occurrence of macrophytes before and after the invasion of water hyacinth is highlighted. The dynamics of water hyacinth, control measures employed for its control and macrophyte succession are also mentioned.
Management and Ecology of Lake and Reservoir Fisheries | Wiley
(Wiley, 2002-02) G.Cowx, Ian
In this comprehensive edited book, international experts in fisheries management and ecology review and appraise the status of lake and reservoir fisheries, assessment of fisheries yields, trophic ecology, rehabilitation and conservation, including a special section on African lakes where so much information of huge relevance to fisheries managers is now available . Contributions from around the world. Carefully edited by internationally respected editor. Has been generated from acclaimed HIFI Symposium.
Systematics and distribution of zooplankton in Lake Victoria basin, Kenya
(AQUA DOCS, 2006-01) Mutune, Masai; Omondi, Reuben; Owili, Monica
Zooplankton samples were collected, using a 60µm nansen net, from Lake Victoria and adjacent water bodies with emphasis being placed on the different habitats within the ecosystems. A total of 116 species were identified, 63 rotifers, 24 cladocerans and 29 copepods. A number of these were new records for the zooplankton fauna for the country.
Groundwater overdraft vulnerability and environmental impact assessment in Arusha
(Springer, 2006-07-11) Ong’or, Basil T. I.; Cang, Shu Long
A simple approach is proposed for identifying areas vulnerable to groundwater overdraft. The methodology utilizes GIS techniques to analyze and evaluate controlling factors in areas with little data. The proposed methodology was applied in Arusha. Water demand in Arusha Municipality and its environs has increased to about 5.3% annually since 1999. Groundwater levels have declined. The aquifer hydrogeological variables were evaluated for impact to potential groundwater overdraft by overlay and index techniques. The spatial distribution of overdraft vulnerability was discussed. The northwestern part of Arusha is the most vulnerable to overdraft and possible serious environmental impacts. The Loruvani area has the most potential for aquifer development due to its permeability, high recharge rate, massive aquifer thickness and low drawdown.
Environmental impact assessment of risk associated with groundwater overdraft remediation in cone of depression, Jining, China
(Springer, 2007-01-12) Ong'or, Basil; Shu, Long-cang; Liu, Pei-Gui
In this paper, a simple scenario and probabilistic approach is used to assess the potential groundwater risk due to proposedoverdraft remedial actions in cone of depression, Jining City, China. Focusing on the concentrations of Chloride ions (Cl−) and total hardness (TH), the impact of artificial recharge and reduced pumping on groundwater quality and quantity is analysedby using the three-dimensional finite difference groundwater flow and transport model, Visual MODFLOW, to simulate groundwaterflow and transport within the study area based on scenarios, and utilizes SURFER software to map risk levels. Although 5,10 or 15% reduced pumping with artificial recharge leads to more decrease in Cl− and TH concentrations than the 25%, less volume increase is achieved for the remediation of land subsidence and other environmentalproblems in the cone of depression. The Cl− concentrations in recovered groundwater are within the desired concentration of 200mg/l; however, TH in some cases are abovethe maximum permissible limit of 500mg/l, with an exceedence probability of about 0.67 for recharge and recharge with reducedpumping at 25%. The presence of fractures and hydrogeological complexity greatly determines impacts of remediation, and the22% reduced pumping with artificial recharge offers an optimum strategy for overdraft remediation in the Jining cone of depression.
Spatial and temporal changes in the distribution of Rastrineobola argentea in Lake Victoria
(Taylor & Francis group, 2007-11-26) Tumwebaze, R.; Cowx, I.; Ridgway, S.; Getabu, A.; MacLennan, D. N.
Following recent changes in the ecosystem of Lake Victoria resulting from the introduction of Nile perch, Lates niloticus, in the 1960s, there is urgent need for information on which to formulate rational exploitation and management of the fisheries resources. This paper presents information on the biomass and distribution of dagaa, Rastrineobola argentea, the second most important commercial species in Lake Victoria. Data were collected during five acoustic surveys conducted between 1999 and 2001, using a Simrad EY500 echo–integrator with a 120 kHz split–beam transducer. Fish samples were collected using a frame trawl, bottom trawl and pelagic trawl, all lined with 5 mm mesh size netting. The mean total biomass of R. argentea in the lake was 476,902 ± 339,308 t at an average fish density of 7.3 ± 5.4 t km −2 in the sampled area. Potential yield was estimated at 581,584 ± 305,377 t (8.5 ± 4.4 t km −2 ). The majority of the biomass of R. argentea (an average of 68%) was distributed in waters of more than 40 m depth. The biomass of R. argentea increased progressively over the survey period, probably as a result of decreased predation pressure by Nile perch.
The role of the Yala swamp lakes in the conservation of Lake Victoria region haplochromine cichlids : Evidence from genetic and trophic ecology studies
(Wiley, 2008-05-04) Abila, Romulus; Salzburger, Walter; Ndonga, Millicent; Owiti, Dickson; Barluenga, Marta; Meyer, Axel
Lake Kanyaboli, an isolated satellite lake of Lake Victoria, has been suggested as a potential refugium for haplochromine cichlids that have gone extinct in the main basin of Lake Victoria. Mitochondrial DNA (mtDNA) molecular markers, as well as feeding ecology studies, were employed in this study to re-evaluate the evolutionary and ecological significance of six common Lake Kanyaboli haplochromines. The mtDNA marker revealed high genetic variability within four of the six haplochromine cichlids. Five haplotypes were discerned in Astatoreochromis alluaudi (n = 27), seven in Lipochromis maxillaris (n = 29), five in Astatotilapia nubila (n = 12) and 11 in the endangered Xystichromis phytophagus (n = 205). A haplotype genealogy suggests that Lake Kanyaboli harbours mtDNA haplotypes that could have been lost or not sampled in Lake Victoria, or could have arisen in situ. Lipochromis maxillaris appears to have undergone a recent demographic expansion. The pairwise FSTs indicated that only the comparison between X. phytophagus and A. nubila led to a non-significant FST value. All other comparisons were significant at the 0.01 level, indicating the genetic distinctiveness of the haplochromines in the satellite lake. This could suggest that the lake harbours 'pure' relict populations of the haplochromines and therefore that Lake Kanyaboli can be considered a 'genetic reservoir'. Gut content analysis of the six haplochromine species revealed that eight different food items were consumed. No single species fed exclusively on a single food item, but certain food items contributed higher proportions of the fish diet for each fish species. Resource partitioning therefore could be discerned within this haplochromine community. Thus, Lake Kanyaboli and similar satellite lakes provide an opportunity for conservation of both genetic and trophic diversity threatened by introduction of exotics in the Lake Victoria basin. Lake Kanyaboli should be recognized and conserved as important evolutionary significant units for Lake Victoria region haplochromine species.
Environmental impact assessment using FORM and groundwater system reliability concept: case study Jining, China
(Springer, 2008-08-01) Shu, Long; Liu, Pei-Gui; Ong'or, Basil
In this paper, fist-order reliability method (FORM) is used to evaluate the impacts of uncertainties posed by traditionaldeterministic models on the environment in Jining, China. Because of groundwater contamination in shallow aquifer, and anincrease in water demand, the new wells target the confined aquifer with constant pumping rate of 5,000m3/d. Using Theis equation, the groundwater drawdown is analyzed to determine whether the confined aquifer will be contaminated.Although the piezometric level is higher than the phreatic level by 11.0m, the risk of drawdown is still 19.49% when thepumping rate of 5,000m3/d is maintained for 2years. The deterministic model indicates a drawdown of 8.94m which is lower than the maximum tolerancedrawdown of 11.0m. The sensitivity and uncertainty analysis reveal that the model result is more sensitive to transmissivitythan specific yield, while the reliability analysis offers significant information for the decision makers. This approachexposes and minimizes the risk of undesirable consequences such as groundwater contamination.
Groundwater overdraft and the impact of artificial recharge on groundwater quality in a cone of depression, Jining, China
(taylor and francis, 2009-12-03) Ong'or, Basil T. I.; Cang, Shu Long
Groundwater overdraft has led to cone of depression formation in Jining City, China. This paper investigates spatial groundwater overdraft severity by an index and Geographic Information System (GIS) method, and impact of artificial recharge on groundwater quality, by a 3-D groundwater flow finite difference numerical model code MODFLOW, and a solute transport model code MT3D. Hydrogeological and anthropogenic factors were evaluated. Groundwater concentration of chloride ions and total hardness (THD) as a result of artificial recharge were evaluated. The hydro-geochemical formation of the aquifer and recharge water quality greatly impact the groundwater quality. The recharge water must be within high groundwater quality standards.
Application of GIS-Based Spatially Distributed Hydrologic Model in Integrated Watershed Management:A Case Study of Nzoia Basin, Kenya
(Research Gate, 2010) Nyadawa, M. O.; Karanja, F.; Njoroge, T.; Otuoma, Sanya
The overall objective of this study was to study the impact of change of land use / land cover on catchment runoff response using FEWS-Flood Model as the rainfall-runoff conversion model in Nzoia basin, Kenya. Land use / land cover grid data were processed for the years 1986 and 2000 in IDRISI Kilimanjaro environment while both soil data and necessary meteorological data inputs were processed in necessary formats in ArcView. The study revealed that loss of forest cover between the year 1986 and 2000 equaled gain in acreage under cropland land/ woodland mosaic in the same period. Analysis of impact of change of land use/ land cover between 1986 and 2000 also revealed increased peaks in resulting hydrographs as a result of increased acreage under crops and reduced forest cover for same storm characteristics. This has given a rationale to recent increased flood disaster in the basin. Key Words: Nzoia, Integrated watershed management, USGS SFM, land use, land cover
Relative abundance of mosquitoes and snails associated with water hyacinth and hippo grass in the Nyanza gulf of Lake Victoria
(Wiley, 2010-09-16) Ofulla, A.; Karanja, Diana; Omondi, Reuben; Okurut, T.; Matano, A.; Jembe, Tsuma; Abila, Richard; Boera, Priscilla; Gichuki, John
This study was conducted from September to December 2008 to investigate the relative abundance of malaria vectors and schistosomiasis host snails associated with aquatic weeds in Nyanza Gulf (Lake Victoria). Larval and adult’s stages of mosquitoes, lakeflies and snails were collected and identified with standard entomological and malacological techniques. The relative species composition and abundance of fish associated with macrophytes were also determined. Physico-chemical parameters were determined with standard analytical methods. Community-based surveys were also conducted, using standard questionnaires, focused group discussions and direct observations. The results of this study indicated that the abundance of malaria-causing mosquitoes was low, accounting for only 0.4% of the total number of mosquitoes and lake flies collected from the gulf. Lake flies (Chaoborus and Chironomus spp.) were the most abundant flying insects associated with aquatic macrophytes (84.2%), followed by Culicines Culex spp. (12.2%) and Aedes spp. mosquitoes (3.2%). Biomphalaria sudanica and Bulinus africanus, the two most common hosts for schistosomiasis in the gulf, were detected in both types of macrophytes, but were most significantly attached to water hyacinth (P < 0.0001) and hippo grass (P = 0.0003). There were significantly fewer snails attached to the hippo grass, compared with those unattached in the open water (P < 0.05, GENMOD). Different habitats exhibited low Secchi disc transparency values, but elevated total phosphorous (TP), total nitrogen (TN), chlorophyll-a concentrations, as well as algal cell counts. Furthermore, Oreochromis niloticus and Haplochromine fishes were more abundant in water hyacinth mats compared with hippo grass mats and open-water habitats. The low mosquito abundance indicated that the sampled habitats were unsuitable for mosquito breeding, likely attributable to water turbulence and/or predation by larvivorous fish. The strong association between B. sudanica and B. africanus and aquatic macrophytes, and the observation that local communities perform many lakeshore-related activities that bring them into contact with water, can potentially lead to a higher prevalence of schistosomiasis in the Nyanza Gulf region.
Geo-electrical resistivity and groundwater flow modells for characterization of a hardrock aquifer system
(Semantic Scholar, 2012) K’Orowe; Rangarajan
In the present study, focus is on evaluation of the utilization of geo-electrically derived hydraulic parameters and processes in groundwater flow modelling. Aquifer parameters and processes data, namely, formation factor, transmissivity and natural recharge at some locations are correlated linearly with geoelectrical resistivity of a hard rock aquifer in the Jangaon sub-watershed, Hyderabad, India. Petrophysical relations have been used to transform resistivity distribution into transmissivity and natural recharge distribution. The coherence of geo-electrically derived parameters has been tested by integrating them into a groundwater flow model. This was performed using MODFLOW codes during one hydrologic cycle within two time periods; time period one coinciding with the rainy season, when there is recharge to the aquifer with no pumping occurring at observation boreholes. During the second time period, dry conditions prevail, hence there is no recharge but observation boreholes are pumped. At the end of the simulation period, simulated groundwater water heads were compared with the observed hydraulic heads and a close match between the observed hydraulic heads and simulated heads has shown the reliability of geo-electrical data as a means of estimation of hydraulic parameters.
INTEGRATED WATER AND NUTRIENT MANAGEMENT IN IRRIGATED KANO PLAIN’S PADDY FIELDS, KENYA
(University of Eldoret, 2012) Kemei, Kipruto Maxwell
Water shortage and paddy field nutrient (nitrogen) depletion are major constrains to sustaining and increasing rice (Oryza sativa L.) production in Kano plains, Kenya. Scarcity of water resources and increasing cost of conveying to paddy field calls for proper in situ water management towards reducing volume used per unit rice field. On the other hand high cost of commercial fertilizer makes rice farming expensive to many peasant rice farmers. As a response, an experiment was initiated with an objective to study effect of local inputs (rice straw, Azolla and fish culture- droppings) on some soil physico-chemical properties, nitrogen uptake, rice growth, yields and paddy field water requirement, when the inputs were used as nitrogen supplement to farmers’ practice (58kgN-Urea/ha).The experiment was conducted in West Kano Irrigation Scheme Kisumu County, consisting of three treatments and a control (farmer’s practice), laid out in a Randomized Complete Block Design (RCBD), replicated three times. Sample collection and characterization were done using standard procedures. Data was managed using Microsoft Excel software. Analysis of variance between treatments on the mentioned soil and rice attributes was carried out using General Statistical (GENSTAT) computer software and means separated with LSD (p≤ 0.05). Significant difference in nitrogen uptake (p≤ 0.05) were obtained in treatments; Azolla>fish-culture>farmers’ practice> rice straw. This was reflected in rice biomass accumulation and yield of 4.3, 3.8, 3.6 and 3.0 ton /ha respectively. Effective hydraulic conductivity induced by change in soil bulk densities was significantly different (p≤ 0.05) in the treatments; rice straw>Azolla>fish-culture>farmers’ practice, that of straw being exceptionally higher translating to treatment with the highest paddy-field water requirement (20.3 Megalitres/ha). The paddy field water requirements of Azolla and Fish-culture were significantly lower due to other factors that affected paddy- field water balance. Azolla and fish-culture treatments were considered to have potential to increase paddy rice production in Kano plains.
Water Hyacinth Eichhornia crassipes (Mart.) Solms-Laubach Dynamics and Succession in the Nyanza Gulf of Lake Victoria (East Africa): Implications for Water Quality and Biodiversity Conservation
(The Scientiﬁc World Journal, 2012-04-19) Gichuki, John; Omondi, Reuben; Boera, Priscillar; Okorut, Tom; Matano, Ally Said; Jembe, Tsuma; Ofulla, Ayub
This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes, Ipomoea aquatica Forsk., and Enydra fluctuans Lour., during early stages of succession. This is followed by hippo grass Vossia cuspidata (Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities.
Water Hyacinth Eichhornia crassipes (Mart.) Solms-Laubach Dynamics and Succession in the Nyanza Gulf of Lake Victoria (East Africa): Implications for Water Quality and Biodiversity Conservation
(Scientific World Journal, 2012-04-19) Gichuki, John; Omondi, Reuben; Boera, Priscillar; Okorut, Tom; Matano, Ally Said; Jembe, Tsuma; Ofulla, Ayub
This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes, Ipomoea aquatica Forsk., and Enydra fluctuans Lour., during early stages of succession. This is followed by hippo grass Vossia cuspidata (Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities.
Hydrogeophysical Parameters Estimation for Aquifer Characterisation in Hard Rock Environment: A Case Study from Yaounde, Cameroon
(Scientific Research, 2012-08-02) Teikeu, William Assatsé; Njandjock, Philippe Nouck; Bisso, Dieudonné; Atangana, Quentin Yene; Nlomgan, Jean-Paul Sep
Detailed local geological and hydrogeophysical investigations were carried out for the aquifer in Yaoundé, Cameroon to delineate the architecture of different subsurface geological horizons using lithologs and generated vertical electrical sounding (VES) data. An attempt has also been made to estimate aquifer transmissivity from resistivity data. The transmissivity of the uncon?ned aquifer was computed by determining the Dar-Zarrouk parameters (longitudinal unit conductance and transverse unit resistance) and were compared with the actual field transmissivity. The results showed a direct relation between aquifer transmissivity and transverse resistance. The relationship established has therefore, been generalized in the study area in order to evaluate hydraulic conductivity and transmissivity at all the points where geoelectrical measurements have been carried out. This generalization allows one to derive maps of the product Kσ and transmissivity in the study area based on geoelectrical measurements. These maps are important in future modelling processes oriented towards better exploitation of the aquifers.
Development and application of micro-field rain-harvesting technologies
(ResearchGate, 2013) Mo, F.; Zhou, H.; Wang, J.; Zhao, H.; Zhang, H.; Wu, S.; Chen, Yinglong; Yang, T.; Deng, H.; Batool, A.; Wang, R.; Nguluu, S.N.; Li, F.; Xiong, Y.
In the typical rainfed agricultural regions of China such as the Loess Plateau, average annual rainfall ranges from 300 to 550 mm. Spatial and temporal distribution of rainfall is extremely uneven and there is a serious dislocation between water supply and demand during critical period of crop water requirement. Developing efficient rain-harvesting farming technology is critical for local food production. Over last three decades, micro-field rain-harvesting and evaporation-preventing techniques have gradually become major tillage management approaches in rainfed agricultural areas of the Loess Plateau. Since 1980s, various micro-field rainwater-harvesting techniques have been developed with integrating mulching (film, gravel or straw) practices in the Loess Plateau. These techniques include ridge-furrow cultivation with half, whole or without mulching, and flat planting with mulching. Especially, large-area extension and application of the techniques for ridge and furrow with whole plastic mulching has played a vital supporting role to ensure the increase in grain yield per unit area in a large extent in dry areas of northwest China. Currently, this farming technique was widely recognized as an optimal pattern of micro-field rain-harvesting technology. In general, micro-field rainwater-harvesting mulching technology was designed as alternating furrow and ridge array with partly or fully mulching on the topsoil. The ridge and the furrow were used to harvest and collect runoff, respectively, and crop was planted in the furrow. This paper reviewed the evolution process of micro-field rain-harvesting and evaporation techniques and their influences on farmland ecosystem. We also summarized the effects of ridge-furrow mulching modes and sowing methods on crop yield formation, water use efficiency, crop ecophysiology, soil quality, soil microbial, weeds, plant diseases and insect pests, mulching residues and crop phenology. In addition, enhanced productivity and efficiency, potential ecological risks of these techniques and their interactions were analyzed. As for design of ridge and furrow specification, the width ratio between ridge and furrow varied from crop type, rainfall amount to air temperature. In most areas of the Loess Plateau, the optimal width ratios between ridge and furrow were 60 cm: 40 cm and 60 cm: 60 cm for potato and corn, respectively, to achieve the greatest grain yield. Among a variety of mulching materials, plastic film was the most widely used, mainly because it displayed the advantages in evaporation prevention, yield improvement and low price. Existing studies showed that plastic mulching would increase soil surface temperature and lead to better performance in grain yield and dry matter accumulation particularly in those areas with high elevation and low accumulated temperature. In the areas with annual air temperature accumulation of less than 5°C, grain yield of plastic-mulched corn was up to 11 times more in comparison with that of traditional flat planting system. In addition, this technique increased the residues of root system in soil, and accordingly enhanced population sizes and biological activities of soil bacteria and fungi. Furthermore, crop growth period was shortened by 7-15 days as a result of application of this technology in the Loess Plateau. However, plastic film mulching for years brought about increased plastic residues in soil and accordingly led to soil pollution and related environmental problem. Finally, efficiency, sustainability and developmental potential of these techniques were discussed aiming to provide theoretical guidance for sustainable management of rainfed agricultural ecosystem.
The Water Act 2002 and The Constitution of Kenya 2010: Coherence and Conflicts Towards Implementation
(International Journal of Disaster Risk Reduction, 2013) Kanda, Edwin; Taragon, John; Kimokoti, Susan; Waweru, Sam
The water Act 2002 provides for Integrated Water Resources Management along the River Basin that is the best practice worldwide and in accordance with Dublin Principles. Prior to reforms in the water sector, water supply and sanitation and water resources management in Kenya faced huge challenges among them being institutional weaknesses, inadequate funding, conflicts due to overlapping roles and responsibilities of key public sectors in the water Act. The constitution of Kenya 2010 recognizes water and sanitation services as a basic right. Before the enactment of the new constitution, the old constitution did not provide for water provision as basic right. This paper presents an analysis of the water Act in relation to the new constitution of Kenya and the challenges facing its implementation. Ways of harmonizing the water Act with the new constitution are explored. It is imperative to note that the Water Act does not recognize water as a basic right and therefore some sections of the Act have to be amended to conform to the constitution which enshrines it in the Bill of Rights.

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