Hydrological Impact of Deforestation in the Central Himalaya
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Hydrology ofMountainous^4reoi (Proceedings of the Strbské Pleso Workshop, Czechoslovakia, June 1988). IAHS Publ. no. 190, 1990. Hydrological impact of deforestation in the central Himalaya M. J. HAIGH Geography Unit, Oxford Polytechnic Headington, Oxford, England J. S. RAWAT, H. S. BISHT Department of Geography, Kumaun University Almora, U.P., India ABSTRACT Deforestation is the most serious environmental problem in Uttarakhand, home of the Chipko Movement, the Third World's leading nongovernmental organization (NGO) dedicated to forest con servation. This group exists because of the rural people's concern for the loss of forests and their personal experience of the envi ronmental consequences. Despite this, it has become fashionable for scientists from some international organizations to argue there is little evidence for recent deforestation, desertification, acce lerated erosion and increased flooding in the region. This paper tries to set the record straight. It summarizes results collected by field scientists in Uttarakhand. These data reinforce the popu lar view that deforestation and environmental decline are very ser ious problems. Preliminary results from the Kumaun University/Ox ford Polytechnic instrumented catchment study are appended. This catchment is set in dense Chir (Pinus roxburghii) forest on a steep slope over mica schist in a protected wildlife sanctuary on the ur ban fringe at Almora, U.P. The results demonstrate a pattern of sediment flushing associated with the rising flows of the Monsoon. INTRODUCTION Deforestation is the most serious environmental problem in Uttar akhand, the Himalaya of Uttar Pradesh, India (Fig. 1). This tract, which covers nearly 52 thousand km2 on the western borders of Nepal, is home of the "Chipko" Movement, the Third World's leading NGO devoted to forest conservation (Haigh, 1988a). This group achieved international notice through its successful campaigns to persuade the Indian Government to reform destructive forest poli cies and control damaging surface mine operations in the Himalaya, and through its Gandhian approach to development. Chipko exists because of the concern of the rural people, par ticularly the rural women, for the loss of their forests and be cause of their personal experiences of the environmental consequen ces (Jain, 1984). As time goes by, the daily chores of gathering fuelwood and bearing water require longer and longer journeys. As time goes by, obtaining timber to build newly wed children a house, becomes more and more difficult. Worse, each monsoon brings the threat of more severe problems. Bhatt (1980) writes: "In Chamoli District alone there are at least 450 villages where homes, fields 419 M. J. Haigh et al. 420 and forests are crumbling due to the repeated visitations of floods and landslides". The symptoms of environmental degradation every where. Despite this, it has become fashionable for scientists from some international organizations to argue that there is little real evi dence for accelerated recent deforestation, desertification, ero sion, or an increasing flood hazard in the Himalaya (Pearce, 1986; Ramsay, 1987; Hamilton, 1987). These writers tend to stress the variability in ("uncertainties surrounding") the data which is pro duced by researchers in the Himalaya (Ives, 1987; Thompson & War- burton, 1985). They base their own generalisations on studies in the Middle Hills of Nepal. The Kathmandu area has one of the long est histories of development in the Himalaya and one which con trasts very sharply with the much larger tracts of the Himalaya where development has become a problem during the last century. These writers also tend to base their hydrological observations exclusively on the publications of foreign workers in Nepal, which has yet to establish a major hydrological station. Writings from India, Pakistan, and even other mountain areas tend to be ignored. There are, of course, very good reasons why friends of Nepal might not wish that nation to be linked to flooding and sediment pollution problems which extend beyond its boundaries (Chalise, 1986). However one may sympathise with that wish, the scientific evidence is different. Further, it is critical to the well being of neighbouring nations, with large mountain areas of their own, to be aware of the problems which exist in their own hill country and to channel their resources towards the solution of those problems. This paper attempts to set the record straight. It is a summary of the results collected by research workers in Uttarakhand, India. These results tend to support the disturbing images of environment al degradation put forward by most NGOs and independent environmen tal researchers of the Himalayan region. The paper also includes a note on the first data from the first hydrological monitoring sta tion in the Central Himalaya, which has been established by Kumaun University and Oxford Polytechnic at Almora. THE ENVIRONMENTALIST'S MODEL OF ENVIRONMENTAL DECLINE IN THE HIMALAYA Originally, the Himalaya of Uttarakhand were largely mantled with trees. However, the expansion of population during the British period caused the forests to become stressed by the needs of the subsistence economy. British attempts to conserve the forest re sources through closure resulted in a massive increase in pressure on those forest lands left in local control, forest destruction through political protest, and the alienation of local people from any feeling of responsibility for the forest resource (Pant, 1922). Military demands during two world wars, the growing timber and fuelwood demands, and tree theft (which may account for 25% of all timber exploitation in the hills) all added to the degradation of the forests. To this has been added the growth of the road network which has both directly and indirectly contributed to forest dest ruction through clearance, landsliding and facilitating tree theft 421 Hydrological impact of deforestation 78 80 82 84 Fig. 1 The Uttar Pradesh Hill Region. 1) Uttarkarshi, 2) Dehra Dun, 3) Tehri, 4) Chamoli, 5) Pauri, 6) Pithoragarh, 7) Almora, 8) Nainital. (Haigh et al., 1987; Haigh 1983, 1984). Meanwhile, the population of just 4.787 million (1981) continues to expand at a rate of around 2.3% p.a. In its wake, agricultural extension proceeds at about 1.5% p.a. and livestock at about 0.18 cattle units p.a. (Shah, 1982). So, over the years, the tree cover has become depleted. Once, the tree canopy, the undergrowth and particularly the leaf litter, intercepted the bulk of the incident rainfall which dripped and seeped slowly to a deep, open structured soil with a large and well developed biota. Little remained at the soil surface to cause sur face runoff. However, a proportion of the water which infiltrated was trapped by the vegetation and returned to the atmosphere as évapotranspiration. The remainder soaked to the groundwater to feed springs, seeps, and to provide the base flow of perennial streams. Then, during the last century, and especially during the last few decades, the mountains suffered severe forest degradation, much of which was due to processes with origins outside the mountains themselves: colonial, commercial and national, some of which was due to pressures building up in local communities. The forest cov er of the hills was reduced precipitously and that which remained suffered thinning due to lopping for timber. Overgrazing and burn ing to improve pasture prevented regeneration. Now, there remained much less vegetation to protect the soil. The soil became more vulnerable to erosion and more easily compac- M. J. Haigh et al. Ail i U T3 > CO CM Q) C O o o d > tt! rH d d O i-H tu C c o O -H -O -H 4-1 C -t-1 Dux) m co CM Cs) 3 m o) c m co r- m o « u u M 0) U O) *-> > C CM CM ON •* CM CO (-- r- 00 ON O ON a. •H C <u o o o 00 ON n r- m 00 00 .-H a. CM aoi I co ON ON s > d d d d d d (U O *-> r-\ VI <4-l I bo m D O iH •o- i-H CM O CM M rH r- ON 00 00 00 00 xï td E-l <4-l I •* ON m ~fr O C0 G 00 r-. t-H VO •* m e CM t-H ON CO CM <-H e a. o O co 00 t-< co ON c s^ ON 00 ON 00 (13 co r» U 0» d m (8 ni as O o 00 + (0 X) 01 ai Q) ai ai u c C o x x o <ti s 423 Hydrological impact of deforestation ted. The reduced vegetation cover allowed more water to reach the soil more rapidly and returned less to the atmosphere. Surface runoff began to occur more frequently and, as it did so, rates of erosion began to rise. Erosion rapidly reduced the depth of the soil and thus its capacity to store water. As time passed, more and more water ran across the ground surface, and less and less soaked into the ground. As a result, the groundwater table became lowered, springs ran dry and the landsurface suffered desertifica tion. As the tree roots in the soil rotted away, the steep hill sides became prone to an increased frequency of landsliding. Soil mobilised by erosion and rubble from landslides was dumped in streams and river channels causing their beds to aggrade rapidly. Perennial streams became buried beneath channel debris. Perennial streams became ephemeral due to the decline in the water table and reduction in base flow. Flooding became more serious because of the increased volume of water in the environment, because of the increased frequency and volume of surface runoff and because of the rising levels of affec ted river beds. Landsliding became more frequent because of the toe erosion caused by the increased monsoon floods, because of deforestation and because of road construction.