Exploring the Spatial Variation of the Relationship between Land Use and Water Quality in a Drainage Basin Using Geographically Weighted Regression

Abstract

The focus of this study is to determine the relationship between land use and water quality in the
River Mu drainage basin for effective water quality management. Various land uses in the study
area were identified and mapped using Landsat 8 OLI of 2016. Water samples were also collected
from 112 sample sites using Stratified Random Sampling methods. The samples were analysed in
terms of physicochemical parameters using standard methods. The results of land use and water
quality parameters were regressed using Geographically Weighted Regression (GWR) to
determine whether there exist spatially varying relationships. The results revealed that the local
R
2
values varied between 0.0 and 0.5, indicating a weak relationship between land use and water
pollution, except for mixed forest and pH which recorded local R2
values of 0.7 towards the
western region of the study area. This shows that the relationship between the two variables varied
spatially across the drainage basin. The one-sample Kolmogorov Smirmov test-p<0.05 revealed
that there were significant differences in pH (0.00), EC (0.00), turbidity (0.001), TDS (0.048), DO
(0.003), NH4
+ (0.002), Ca2+ (0.00), Cl-
(0.036), Fe3+ (0.00) and Cr2+ (0.039) across the different
sample points, whereas K+ (0.134), PO4
3-
(0.715) and NO3
-
(0.501) were not significantly different
across the different sample points. The study recommended that the procedure for water
management be localized to sub-catchment and basin levels, to provide adequate attention to each
sub-catchment depending on the level and nature of pollution identified