Influence of Land Cover Changes and Climatic Variability on Discharge Regime of Njoro River Catchment in Kenya
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Date
2019
Authors
Mwetu, Kennedy Kitonga
Journal Title
Journal ISSN
Volume Title
Publisher
Scientific Research Publishing
Abstract
This study analyzed influence of land cover changes and climatic variability
from 1973 to 2000 on discharge regime of Njoro River Catchment in Kenya.
Analysis focused on hydro-meteorological data of 1977-1984 (Period I) and
1992-2000 (Period II), which are the periods found with available data and
Landsat imageries for the same periods. Results show a downward trend of
annual discharge that corresponded to increased deforestation. Forest area
decreased by 25% while open fields combined with grasslands increased by
58% between the two periods. Discharge in Period I was 36% (0.23 m3/s or 82
mm/a) higher than Period II whereas increase of annual temperature
(0.75˚C) between the two periods was significant (P < 0.05) but decrease in
rainfall (24.87 mm/a) was not significant with effect of 25% deforestation.
Statistical analysis of both four rainy and four dry years in the two periods
showed that: 1) mean monthly discharge in Period I was not different (P <
0.05) and variability in decreases was higher (z-score: 4.60 > 3.98) in rainy
years compared to dry years, and 2) mean discharge in Period II was different
(P < 0.05) and variability in decreases was higher again in rainy years than
dry years (z-score: 4.78 > 4.77). Influence of climatic variability alone accounted for 25% (0.06 m3/s) on reduction of discharge while human activity
mainly deforestation accounted for 75% (0.17 m3/s) on reduction of discharge
in Period II. This implies that land cover changes were largely responsible for
decrease in discharge and therefore, intervention measures of restoring forest
cover are recommended for Njoro River Catchment.
Description
A research article published in Open Access Library Journal
Keywords
Agricultural Science, Ecology, Environmental Sciences