Analysis of Runoff, Infiltration Rate, Sediment Release and Nutrient Drain From Four Vegetation Types in South Kinangop Forest, Nyandarua County
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Date
2014
Authors
Chege, N. J.
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Publisher
Kenyatta University
Abstract
Availability of quality water supply is essential for a healthy nation and development. Water resources in Kenya are threatened by overuse, misuse and pollution as a result of destruction of vegetation in the watersheds. It is recognized that water quality and quantity factors are strongly influenced by forests. Degradation of water resource therefore causes large chemical consignments for water treatment. This study analysed the performance of four vegetation types in south Kinangop forest station of the Aberdare ranges in Nyandarua County on run-off release, nutrients drain, infiltration rate and sediment load release. The main objective of the study was to assess the role of the four selected vegetation types on run-off discharge, infiltration rate, sediment load discharge and nutrient losses. The experiment employed selection of four forest blocks and laid runoff samplers replicated three times in each type. The four vegetation types were Bamboo, Grassland, Cypress plantation and Natural forest. The runoff plot size measured 8x5m plots. The slope and the vegetation status on each plot were assessed and recorded. Rainfall data was collected and recorded from a central position. One percent of the runoff was collected and quantified from the calibrated sampler after a successful down pour overnight and analysed. Samples of leachates were retained for sediment load, quality and nutrients analysis in the laboratory at the end of the experiment. Soil samples from the four vegetation types were collected at 15cm with an auger bit and analysed for pH, Nitrogen, Potassium and Phosphorous (NPK). Infiltration rate was assessed in each of the vegetation types and data tabulated. Sediment load analysis was done from extract of leachates collected to ascertain its magnitude on each of the vegetation type. The data was run through GenStat 16th version (32bit) and Microsoft Excel 2007 statistical packages. The results (p˂0.01) on runoff, infiltration rate, sediment load and nutrient drain were statistically significant with an exception of phosphorous had a value (p=0.315) which is greater than the tabulated p>0.05. This indicates that Phosphorous is not influenced by the vegetation type. Cypress plantation had the highest sediment load release of 0.3 tons per hectare followed by Natural forest, Bamboo and Grassland had the least. These results indicated that different vegetation types had influence on the run-off, nitrogen and potassium drain, infiltration rate and sediment load release. Based on the sediment load, turbidity levels and the Phosphorous drain, the order of merit was grassland, bamboo, natural forest and cypress plantation. Although bamboo was ranked second it outweighs grassland in terms of multiple utility. Bamboo is therefore best for countering sediment load, enhancing infiltration rate, reducing nutrient drain and stabilizing soils along degraded catchments
Description
Department of Geography, 107p. 2014