Browsing by Author "Githae, E.W."

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Effects of Agricultural Nutrients Influx on Water Quality in Thiba River basin, a sub-catchment of Tana River Basin in Kirinyaga County, Kenya
(East African Nature & Science Organization, 2022-04) Njue, J.M.; Magana, A.M..; Githae, E.W.
Excessive enrichment of waters with nutrients and the associated adverse biological effects leads to eutrophication, which is one of the major environmental problems across the world. Various studies have revealed the overuse of inorganic fertilizers to increase agricultural productivity in Kenya contributes to pollution of water bodies. In order to meet increasing demand for clean water, sustainable use and conservation of available water resources is therefore paramount. This study was done to find out effects of agricultural nutrient pollution in Thiba River, a sub-catchment of Tana River Basin, located in Kirinyaga County, Kenya. The study area was divided into four distinct agro-ecological zones based on different anthropogenic activities. Ecological survey design was used in the study. Sampling was done during the wet and dry season. Water samples were analysed for temperature, transparency, pH, electrical conductivity (EC), salinity, total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD), phosphates, nitrates, nitrites, ammonia, and toxic microalgae. All parameters showed both spatial and temporal variations with statistically significant differences (p˂0.01). Temperature of the river ranged from 14.57 0C to 28.08 0C due to climatic changes along the agro-ecological zones. The pH ranged from 7.02 to 8.51. The DO values decreased from the highlands to lowland within the range of 9.00 mg/l at the reference site to 5.43 mg/l at the most polluted site. EC ranged from 20.54 μScm-1 at the reference site during the wet season to 251.2 μScm-1 at the rice irrigation scheme site during dry season. The TDS ranged from 16.9 ppm at the reference site to 167.05 ppm at the most polluted site. Salinity also had a high variation with a range of 0.01 ppt at the reference site to 0.07 ppt at the most polluted site. The highest values of BOD (3.49 mg/l) were recorded at the rice irrigation scheme during the wet season and the lowest (0.22 mg/l) at the forest edge reference site. The lowest levels of NH4, P, NO2 and NO3 were recorded at the forest edge reference site at 1.088 μg/l, 1.177 μg/l, 0.217 μg/l and 0.148 μg/l respectively during the dry season while the highest values for the same nutrients were recorded at the rice irrigation site at 11.439 μg/l, 4.933 μg/l, 1.518 μg/l and 2.721 μg/l in the same order. There was a high peak of all nutrient levels at the rice irrigation scheme zone which was attributed to the extensive use of inorganic fertilizers. Dam water samples were analysed for members of Cyanobacteria group of microalgae which are bio-indicators of eutrophic waters. Out of the seven members of this group that were identified four were toxic genera. These were Nostoc, Oscillatoria, Anabaena and Microcystis.During the wet season Nostochadthe highest population followed by Oscillatoria and Anabaena.No Microcystis was observed during the wet season. There was a steady increase of all the genera during the dry season with Microcystismaking appearance. Microcystisand Oscillatoriahad a very high correlation. This study concludes that various anthropogenic activities especially agriculture along the study site are the main factors of Thiba River pollution hence a major threat to human, livestock and aquatic organisms. Environmental protection laws should be enforced by the government.
Socio-ecological impacts of invasive alien cactus (opuntia) in the rangelands of Narok county, Kenya
(Journal of Research in Forestry, Wildlife & Environment, 2017-12) Githae, E.W.; Magana, A. M.
Many cactus species have been introduced in the Kenyan rangelands and their subsequent spread have had devastating effects on the ecosystem services. Opuntia stricta is the most widespread and forms dense impenetrable thickets that negatively impact on rangeland livelihoods and resources. This study assessed the impact of O. stricta on rural livelihoods and their environment in Narok County. Data was collected using household surveys, key informant interviews and transect-walks. Results indicate that communities in the region are well aware of Opuntia invasion in the area, which has increased rapidly over the recent past and spreading to various ecosystems. The cause of spread was attributed to planting the species for various purposes, garden throw-outs and floods. More than 70% of the respondents perceived the species as undesirable with negative impacts only. The impacts include denied access to natural resources, reduced productivity and increased threat to livestock and human health. Pasture lands, farmlands and degraded lands were the most invaded areas. Chopping was the preferred method of management but was combined with other mechanical and chemical methods in order to be more effective. Appropriate interventions are suggested to mitigate the negative impacts and improve rural livelihoods and their environment.
Socio-Economic Impacts of Invasive Alien Plant Species of Cactus (Opuntia Stricta) In Ewaso Nyiro Area in Narok County, Kenya.
(Chuka University, 2017) Githae, E.W.; and Magana, A.M.
Several plants have been introduced in Kenya for various purposes. Some have become aggressive and rapidly colonize and out-compete the indigenous vegetation. Among them are the Opuntia (Cactus pear) species, one of them being Opuntia stricta Haworth, which was introduced as an ornamental but has spread widely in natural ecosystems especially in the drylands. However, information about its impacts to livelihoods and the sources of spread has not been well documented. This study investigated the challenges faced as a result of invasion and the factors that contribute to the spread. It was done in Ewaso Nyiro, one of the most invaded areas in Narok County, using questionnaires where a sample size of 50 was purposively selected since the area is not densely populated. Impacts caused by Opuntia stricta invasion included denied access to land, injury to both human and livestock and reduced farm- land and pasture-land, land productivity and the well-being of the community. Although majority of the respondents were not aware of how the species got into their farms, some thought that the main source of spread was due to planting the species as an ornamental and a fence. Others thought that it was spread mostly by floods since new invasions occurred immediately after the rainy season. The most common plants affected by O. stricta invasion were indigenous vegetables such as terere (Amaranthus), stinging nettle (Urtica dioica), African nightshade (Solanum), spider plant (Cleome gynandra) and pumpkins (Cucurbita pepo) since they were mostly found on the fence and farm edges and this heavily impacted on the food security. The main methods used to control were chopping, burning, burying and use of herbicides. These methods posed challenges in terms of practicality, expense and environmental impacts and therefore other sustainable methods should be identified that can assist in control as well as improve livelihoods. This should integrate the reported benefits such as source of food, fodder and medicine in order to sustainably manage the species.