P. B. Shah

Gaining forests but losing ground: A GIS evaluation in a Himalayan watershed

GIS overlay techniques were used to provide a quantitative historic documentation of deforestation and land-use dynamics in the Middle Mountains of Nepal between 1947 and 1990. Deforestation was most critical in the 1960s, but active afforestation programs in the 1980s have reversed the process. In spite of these trends, the degradation problem is more complex. The GIS evaluation showed that 86% of the recently afforested land is now under pine plantations located primarily at lower elevations and moderately steep slopes. In contrast, rainfed agricultural expansion is most pronounced on acidic soils and steeper, upper elevation sites, suggesting marginalization of agriculture. Agricultural expansion coupled with major losses of grazing land to pine forests are the key processes pointing towards major animal feed deficits. An alternative animal feed source is suggested through GIS using a topographically based microclimatic classification to generate a tree-planting map where the optimum ecological conditions for selective native fodder tree species are identified.

A GIS evaluation of land use dynamics and forest soil fertility in a watershed in Nepal

Abstract A geographical information system (GIS) based study was carried out in a densely-populated watershed in Nepal. An evaluation of land use change between 1972 and 1990 indicated that there has been an increase in forest and agricultural land area and a decrease in shrubland and grassland area. GIS techniques were used to produce single and composite fertility index maps, which can be used for problem identification and planning. These maps indicate that forest soil fertility is generally poor in the watershed. GIS was found to be very beneficial in addressing critical resource issues in small watersheds in developing countries.

Human interactions in soil and geomorphic processes in Nepal: the role of soil fertility in degradation and rehabilitation processes

Abstract A GIS approach was used in the determination of soil fertility status in the Jhikhu Khola watershed. The watershed was stratified by topography, climate, soil type and land use using GIS overlay techniques. A (2 × 2 × 2 × 4) factorial approach served as the sampling framework to produce single and combined nutrient deficiency GIS maps. Soil acidity, phosphorus availability and lack of base cations were identified as the key soil fertility issues, with forests having the poorest overall soil nutrient status, followed by rangeland, rainfed agriculture and irrigated agriculture. Nutrient budget calculations revealed significant annual deficits in phosphorus for maizerotations but only minor deficits for rice rotations. The effect of inherited biophysical conditions on nutrient deficits were analyzed statistically and displayed using the GIS overlay method. Poor fertility and annual deficits were linked to erosion and sedimentation by documenting annual erosion losses from rainfed agriculture and degraded areas. Over a 7 year period, typical erosion from maize rotations in rainfed agriculture averaged 19 t/ha annually, while erosion from degraded sites were 75–100 percent higher. Significantly different sediment rating curves were obtained from two micro-watersheds, one with 14 percent and the other 25 percent degraded areas. Annual sediment contributions to the micro-watersheds confirmed that degraded sites increase the suspended sediment load, particularly under lower stream flow conditions. The discharge-sediment regression line was significantly higher during the pre-monsoon period than during the monsoon season. GIS tools were found to be useful in all parts of the analysis.

Phosphorus dynamics and soil P-fertility constraints in Nepal

There are significant differences between the red and non-red soils in the Middle Mountains of Nepal, and inherent differences in the parent materials and soil management seem to have the greatest influence on fertility and P dynamics. The red soils with Munsell Hue color of 2.5 YR and 5 YR, were found to have higher P sorption capacity than the non-red soils (Hue 7.5-10 YR), and the Al (AAO) content was found to be the best predictive variable for P sorption. Using a 2×2×2×3 factorial design and GIS overlay techniques, a P-sorption map for a case study watershed was produced. The results may be used for determining where agricultural intensification with chemical fertilizer applications is most effective. The amorphous Fe and Al content is critical in determining P dynamics, and without high organic matter input, the red soils are highly deficient in available P. Management influences the P-sorption capacity in that the Al (AAO) content decreased in irrigated red soils whereas the Fe (AAO) content increased significantly. Irrigation reduces the amorphous Al content and this results in a 10 to 30% reduction in P sorption. Since most red soils are acidic and are deficient in carbon, the reduction of amorphous Al via irrigation has a positive effect on management by significantly reducing P sorption. The reducing conditions created by flood irrigation during the monsoon season and the addition of exchangeable bases from sediments and irrigation water increase pH values by up to 0.5 units and alter the amorphous Al and Fe content in these soils and, hence, P availability.

EVALUATING MOUNTAIN WATERSHEDS IN NEPAL USING MICRO-GIS

Microcomputer-based Geographic Information Systems (GIS) are proving to be a most powerful tool in land resource evaluation. In this paper, examples on how to use this technology are provided for national, district, and watershed evaluation. At the national level a spreadsheet was developed to determine consumption/production balances for food, feed, and fuelwood using the Land Resource Mapping Project (LRMP) and current population growth data as a basis. With the GIS technique, national maps were produced to indicate districts with surplus, sufficiency, and deficit situations for the three resources for 1981, 1989, and 2000. For Kabhre District, which showed deficits for food, feed, and fuelwood, runs of the model were made to illustrate what would be required to eliminate these deficits. Studies were made to determine how much increase in crop yields, how much population migra- tion, how much livestock reduction, and how much expansion in forest plantations would be needed to arrive at food, feed, and fuelwood sufficiency levels in this district. In all cases, the effort required to achieve sustainable conditions appears to be enormous. Finally, GIS techniques were applied to the Jhikhu Khola watershed where a three-year monitoring program is under way to determine water balances, sediment budgets, erosion rates, and soil fertility changes in five sub-basins and two integrating stations in the watershed. GIS techniques facilitated the production of microclimatic maps of the watershed and these in combination with soil maps can be used to develop an afforestation plan that matches site conditions with desirable tree species. GIS also plays a key role in the selection and extrapolation of sub-basins and in evaluating agricultural land most subject to soil fertility decline.

Assessing Renewable Water Resources and Water Use in Angola

“Nature” is one of the culturally most loaded concepts. It is one of the central concepts for human understanding and structuring of the surroundings (Glacken, 1967). The concept of nature is deeply embedded in our understanding of the world, so deep that we seldom reflect its central role in our thinking. With impulses from symbol theory (Elias, 1991), environmental history (Berntsen, 1994; Nash, 1982) and social sciences (Berger and Luckmann, 1987), this article examines nature, not as a physical reality, but as a symbol of ideas, norms and values in society. “Nature” is understood and interpreted in a historical, social and cultural context.

Prevention, Degradation and Rehabilitation: A New Dilemma in Himalayan Watersheds

Watersheds in the Middle Mountains of Nepal are some of the most intensively used drainage basins in the world and degradation in the form of erosion, soil fertility decline, water quality deterioration and declining water supplies is widespread. If degradation processes are recognised in the early stages, rehabilitation is relatively easy, but rehabilitation of sites in an advanced state of degradation is a formidable challenge. Degraded sites, which cover less than 7% of the watershed area, are responsible for more than 1/3 of the annual sediment budget in the Jhikhu Khola watershed. With a combination of grasses and native nitrogen fixing fodder trees, it proved possible to establish good vegetation cover within a 2-year period. However, rehabilitating soil nutrients is painfully slow and differences in parent material have a great impact on biomass production and restoring nutrients. More attention needs to be directed towards sediment and nutrient budget calculations as a means of recognising the early stages of degradation, and thus facilitating rehabilitation early in the degradation cycle.

Water Management Issues in Middle Mountain Catchments of the Nepal Himalayas: The Downstream Perspective

Middle mountain catchments in the Hindu Kush-Himalayan region are the heavily populated and mainly rainfed headwaters of many smaller, but not less important rivers, and the tributaries of the larger North-South rivers draining the mountain system. The catchments are in a fragile and vulnerable region from the perspective of water scarcity, flooding and soil erosion. It is these catchments which caused the theory of the ”Himalayan Environmental Degradation” (Eckholm, 1976).

Reply to Donald Messerschmidt's Commentary

We welcome the suggestions and comments by Dr. Messerschmidt and we are fully aware that the socio-economic questions have not been addressed in any depth. This can be justified as follows: the aims of the project were to demonstrate to the Nepali planners and government personnel how the national bio-physical resource survey can be interpreted for national land-use planning. We chose the Kailali District to demonstrate some but not all of the land-use options available for development. The Kailali District was chosen not as a model for land-