LAND USE DYNAMICS AND LANDSCAPE CHANGE PATTERN ON THE PATCH DRY AFROMONTANE FOREST HYDROLOGY OF NORTHERN ETHIOPIA

摘要

Land-use is a key factor in hydrological modelling. Land use changes are important aspects of global change and affect regional water cycles, environmental quality, biodiversity and terrestrial ecosystems. This study was performed on the state forest of northern Ethiop. The aim to: (1) evaluate land-cover changes and patch fragmentation in a landscape containing forest patches over (1986-2018) of 32 years and (2) estimate the potential impacts of the land use land cover (LULC) dynamics on hydrological response (3) evaluate the spatial and temporal scales modify various aspects of the climate-vegetation-soil-streamflow system. (4) understand and quantify the hydrological processes in a rapid land use dynamic. Landsat satellite images of TM (1986), TM (2001), and OLI (2018) were used. All images were classified using maximum likelihood image classification technique. LULC and surface hydrological change analysis was carried out using post classification comparison. Soil Conservation Systems Curve-Number model, which is used to extract the curve number for watersheds was then employed to formulate the impact of climate and land-cover changes on hydrological response over a period of 32 years (1986-2018). Results showed that seven LULC classes were successfully captured with overall accuracy ranging from 82.7% to 90.2% and Kappa statistic of 0.822 to 0.924. The classification result for 1986 revealed that cultivated land (44.78) followed by shrublands (32.02%). However, shrub land is becoming the dominant (36.64%) followed by decreasing the rate of cultivated land by (28.68%) with an increasing forest land by (from 7.18 to 18.63%), were the dominant LULC types from 1986-2018. LULC change indicated a rapid reduction in cultivated land during the study period. Observed changes in direct surface runoff, runoff coefficient, and storage capacity of the soil have been partly linked to changes in LULC associated with expanding bare land and built-up areas. This land use change aggravates the runoff potential of the area by a mean of 213.58 mm year~(-1). Therefore, combined effects of climate induced moisture stress and landcover led to water abstraction upstream threatened runoff-response at a rate of 0.86 × 106 m~3 year~(-1). Observed rainfall and modelled runoff showed strong positive correlation of R~2 = 0.707 and p ≤ 0.000. The changes were also common along the slope gradient and agro-ecological zones with varying proportions. Further detailed study is suggested to investigate drivers and consequences of changes and its magnitude on forest hydrology of the dry Afromontane forest landscapes.