| The development of economy and urbanization has caused changes in land use and land cover(LULC)of Ashi river watershed.The effects of change in LULC have impacted on the stream flow of the watershed by changing magnitude of hydrological components.This research therefore,investigated the impact of land use and land cover(LULC)changes on hydrology in the Ashi river watershed,and how sustainable land use management(SLM)practices/technologies could be considered as a solution to pollution in Ashi river.Land use and land cover distribution of the watershed was mapped and changes analyzed using satellite images,from 1990 to 2014.Markov-cellular automation model was used to predict future LULC of the watershed,based on worst case and best case scenarios.The patterns,dynamics,processes and intensity of the LULC change were also investigated using intensity analysis(IA)approach.Soil and water assessment tool(SWAT model)was adopted for the hydrological assessment.A survey-based instrument approach,involving structured questionnaire was used to assess how a comprehensive land-based approach(sustainable land use management practices)could be considered as an effective solution for non-point source(NPS)pollution control in the watershed.The results revealed that,urban(URB),water(WAT),agriculture(AGR),open forest(OPC)and other vegetation(OTV)experienced an increment from 1990 to 2014 by 227%,267%,10%,63% and 260% respectively,with urban and agriculture showing consistency in increasing trend and a decline in closed forest(CLC)area by 79%.The predicted LULC for 2030 based on worst-case scenarios revealed more urbanization and agriculture with a potential for expansion to areas near streams and forest,while the best-case scenario indicates a controlled expansion trend of urban and agriculture along the streams,and regeneration of closed canopy forest along the main streams.Findings from the use of Intensity analysis(IA)approach discovers that,the apparent LULC change intensities are not uniform with respect to interval,category and transition levels of IA.The results further show that,swap change accounted for more than 50% of the overall change,which indicate a very dynamic landscape transformation.This implies that reporting only net change in LULC of Ashi watershed underestimates the total LULC change.Transition from closed forest to open forest was found to be a dominant landscape change,as opposed to a random change.Similarly,transition from open forest to other vegetation was also found to be a dominant transition,while transition from other vegetation to agriculture was dominant transition.This suggests a pathway of deforestation from closed forest to agriculture and urban,with open forest and other vegetation as a transitional land covers.Error analysis shows that,hypothetical errors in 13%,19% and 11.2% of the 2000,2010 and 2014 maps respectively could account for all differences between the observed gain intensities and uniform intensity(UI);while errors in 12%,21%,and 11% of the1990,2000 and 2010 maps respectively could account for all differences between the observed loss intensities and the UI.A hypothetical error in 0.6% and 1.6% of the 1990map;1.5% and 4% of the 2000 map;1.2% and 2.1% of the 2010 map could explain divergences from uniform transitions given URB gain and AGR gain during 1990-2000,2000-2010 and 2010-2014 respectively.Evidence for a specific deviation from the relevant hypothesized UI is either strong or weak depending on the size of these errors.Furthermore,the SWAT-based assessment results discovered that,the changes in the basin's LULC has brought about an increment in stream flow(11.5%),surface runoff(86.6%)and water yield(10.5%).On the other hand,the results indicated a reduction in lateral flow(64.9%),groundwater(27.9%)and Evapotranspiration(1%).Stream flow,water yield,surface runoff,lateral flow and evapotranspiration are expected to further increase under both worst-case and best-case scenarios LULC status,but groundwater flow will reduce.Nevertheless,the increment under the worst case is expected to be more than the best-case scenario.Urban,agriculture and close forest contributed mainly in determining the faith of the hydrological processes and therefore are the chief environmental stressors in Ashi watershed.This recommend an urgent need to regulate the urban sprawl and agricultural activities in order to maintain hydrological balance.Findings from the survey-based approach show that,residents of Ashi watershed believe there is low adoption of sustainable land use(SLM)practices within the watershed and strongly linked the low adoption rate of SLM practices to weak capacity building and enforcement of regulations.Occupation and age of the residents are the strongest predictors of SLM adoption rate.Residents connected with farming are more sensitive to the adoption status of SLM.The research recommends policy makers to ensure capacity building and enforcement of regulations that will specifically compel farmers to adopt SLM technologies.This approach would complement other strategies to solve the NPS pollution issue of Ashi watershed.Overall,the approaches including theory,remote sensing,geographical information systems,numerical modelling,processed based modelling,statistical modelling and survey-based approach were integrated to conduct four studies which form the entire research.These studies were considered helpful in providing baseline information between the relationship between LULC change and water resources within the Ashi watershed.In addition,information on how to solve the issue of non-point source pollution of Ashi watershed based on sustainable land use management practices was discovered.This study not only has significant scientific meaning for fully understanding the water pollution causes of Ashi river watershed,but also has shown realistic meaning for the water conservation and comprehensive management of the whole Ashi watershed.At the same time,it could help on integrated basin management and scientific decision with the river which has similar natural conditions. |
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