Abstract
Land Use and Land Cover Change (LULCC) is a major driver of environmental problems like water pollution, decreased soil quality, and natural resource scarcity. Measuring LULCC is necessary to better understand the present condition of watersheds. Time series LULCC mapping using Geographic Information Systems (GIS), high-resolution imagery, and field data collection are effective methods for examining LULCC trends. The Mahadev Khola watershed in Bhaktapur, Nepal, acts as a primary source of drinking water for people living within the Bhaktapur municipalitywhich is dominated by forest at higher elevations and agricultural lands and settlements at lower elevations. The purpose of this study was to observe LULCC dynamics within the Mahadev Khola watershed to better understand the social and environmental problems that can arise in consequence. Time series land use maps were created and analyzed using GIS methods. Responses from a survey of local people, as well as interviews from selected key stakeholders, contribute insight into how past scenarios of land use have influenced-and have been influenced by-LULCC. Significant changes in land use were quantified between 2005 and 2014. Results suggest that in this period, total forest area decreased by 6.25%, cultivation area decreased by 14.28% and settlements increased by 156.25%. Survey and interview responses suggest that much of this change is due to agricultural intensification and an increase in chemical fertilizer and pesticide use. Increased agricultural inputs have increased the potential for river and water pollution and long term soil degradation. Urban expansion and development have led to the contamination of rivers with sewage and solid waste, which has increased health risks for local communities. Although total forest area has increased, the species composition has changed-now primarily dominated by Pinus roxburghii. The result of this is a decrease in river water discharge and increase in soil and water acidity. The results of this study are timely and important for analyzing the dynamics between LULCC and watersheds in order to improve future management efforts in Nepal and the Eastern Himalayan region of South Asia.
Highlights
A watershed is a topographically delineated area that drains rain, snowmelt and ground water into a stream or river-system (Corn et al [1,2])
Solid waste disposal and land use patterns like forest area, croplands, settlement area have transformed the geographical environment (Turner et al [3]), and today, many environmental problems such as water pollution is linked with land use and land cover change (LULCC)
Responses from our field survey with local people suggest that forest cover had decreased due to increase in settlement in upstream region of the watershed
Summary
A watershed is a topographically delineated area that drains rain, snowmelt and ground water into a stream or river-system (Corn et al [1,2]). Solid waste disposal and land use patterns like forest area, croplands, settlement area have transformed the geographical environment (Turner et al [3]), and today, many environmental problems such as water pollution is linked with land use and land cover change (LULCC). Land use and human activities within a watershed can lead to drainage and runoff of anthropogenic substances into water bodies. Studies have shown that watershed quality is greatly affected by human activities through point sources such as wastewater treatment facilities, and non-point sources such as urban and farm land runoff (Sharma et al [5]). Estimating historical LULCC trends is essential in assessing the rate at which change occurs and the problems that result, which can lead to better predictions of future impacts and issues that might occur (Lambin [6]). Heggem et al [10] used a landscape ecology approach in a Louisiana watershed of USA to reveal its increasingly distressed condition over a 20 year period, and causes for this distressed condition were decrease in forest coverage, construction of new roads, stream crossings, etc
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