The sensible and sustainable use of land, water and soil resources is essential to the future development of Nepal. This joint project aims to aid soil and water resource management at the catchment and hillslope scale by providing a greater understanding in Phase 1 (1991-1995) of soil erosion, land failure, hydrological changes and regimes, and water quality. Phase 2 (1996-1999) concentrates specifically on understanding nutrient losses from erosion and leaching on rainfed agricultural land, on which the poorest farmers depend for their livelihoods.
The project was organised by the Royal Geographical Society (with the Institute of British Geographers) in collaboration with the Lumle Agricultural Research Centre and the Soil Science Division of the National Agricultural Research Institute, Nepal.
The Nepal project was established as a long-term monitoring programme within an area vulnerable to environmental degradation. Increasing population pressures within the Himalayas has led to the expansion of its agricultural area. The resulting pressure on already delicate hillslope environments disrupts natural systems operating within the region and makes the area vulnerable to accelerated environmental damage, such as soil erosion and reduction in water quality.
Increasing land clearance and deforestation activity had been assumed in the 1980s to lead to a rapid loss of topsoil, causing productivity to fall and furthering the need for agricultural expansion. Damaging knock-on effects potentially include: increased flood risk during monsoons; reduction in winter stream flows for irrigation; greater erosion and gullying; increased suspended sediment within rivers; declining water quality; and changes within aquatic biology. Further disruption and degradation can be caused through the human response to the situation, with widespread and heavy applications of soil dressings causing the leaching out of minerals and a further decline in water quality. The project was initially designed to provide a scientific assessment of the existence and seriousness of these supposed problems.
In Phase 1 the Likhu Khola catchment, Nepal, (in the Middle Hills region in the north of the Kathmandu Valley), was chosen as an example of a watershed within the southern Himalayas in which these processes could be examined and quantified by an interdisciplinary project team. Based on the data collected the team also hoped to gain greater insights into human/environment interaction and to develop models of the environment that could be used not only to assess future management strategies within the Likhu Khola but also more widely in the region. Such understanding is necessary to underpin future sustainable development. The methodology was based on five subcatchments, with areas from 2-4 km sq., that differed in terms of aspect (north and south facing slopes) and land uses. A control site was largely forested. At each site water levels were recorded and converted to flows using stage-discharge relationships based on spot gauging. In addition to flow measurements, rainfall, pH, conductivity and temperature were also monitored. Weekly samples of rainfall and stream water were collected at the same sites for chemical analysis. At another two sites automatic weather stations were installed, at which a variety of meteorological data were measured; raingauges were located at a further four sites in association with erosion studies. Twenty four erosion plots on all major landuse, five gully sites and four subsurface hydrology plots were established and over 1400 storms monitored. The incidence of landsliding was monitored throughout the study.