Rainfall–runoff-soil and nutrient loss relationships for plot size areas of bhetagad watershed in Central Himalaya, India
Introduction
Eighty per cent of the sediments delivered to the world's oceans each year came from Asian rivers and amongst these Himalayan rivers are the major contributors (Stoddart, 1969). River systems are also the major means of transport of dissolved materials, including inorganic nutrients and contamination, which depends on riverine geochemical and hydrological processes. River geochemistry varies considerably with the type of lithology, topography, hydrology, agricultural expansion and vegetation cover. Understanding this variability in relation to changes in land use and hydrology, will be critical to prediction of the fate and budgets of nutrients in the watersheds (Rai and Sharma, 1998).
Livelihood of the people in the Himalayan region is largely dependent on farming system and especially on subsistence agriculture. The middle mountains of the Hindu-Kush Himalayas (HKH) are densely populated mountain areas in the world, and population of this region is still increasing at an alarming rate. Scarcity of water, both for drinking and irrigation, is a limiting factor for quality life and agricultural production. Fodder is becoming scarce due to degrading forests resources and high population of unproductive livestock. Loss of fertile top soil, due to surface and gully erosion, is a common phenomenon and agricultural land has expanded to areas having marginal soil cover (Hofer, 1998). Although local residents of the region are worst hit by these factors, the deforestation in headwater catchment areas is stated to be the prime cause of frequent flooding in lowlands of Indo-Gangatic plains and sedimentation of reservoirs.
An extensive study was initiated in 1997 in Bhetagad watershed, a tributary to river Gomti in Ganga river system, in order to evaluate the impact of land use on generation of run off and associated soil loss and nutrient export. Plot scale and watershed scale studies have been conducted to investigate the rainfall–runoff-soil erosion processes occurring in the study area.
Section snippets
Review of literature
There have been some attempts to study the dynamics of the natural resources in Himalayas and other mountainous areas of the world (Sharma et al., 2001, Narayan et al., 1991, Singh, 1999, Stewart et al., 1967). Pathak et al., 1984, Pathak et al., 1985 evaluated the fluxes of overland flow, sediment output and nutrient losses from six forested sites in the Central Himalayas during monsoon seasons of 1981 and 1982. Jenkins et al. (1995) collected comprehensive data on major ion chemistry from
Study area
The Bhetagad sub-watershed (Fig. 1) drains an area of 23.52 km2 in the Central Himalaya, which falls within the geo-coordinates 29° 50′ 15″–29° 54′ N longitudes and 79° 34′ 32″–79° 37′ 55″ E latitudes. This watershed in Uttaranchal State of India, having population density 375.2 persons/km2, is a representative watershed of this region. The watershed is characterized by a significant variations in terms of altitude (1,090–2,060 m amsl), slope aspects, forest cover, soil characteristics, land use
Method
Four experimental natural plots (EP1, EP2, EP3 and EP4) of 20 m long and 5 m wide were delineated along the slopes (see; Fig. 2, Fig. 3, Fig. 4, Fig. 5) on four common land use systems having different slope aspects, soil types but almost uniform land slope (ranging between 18.5 and 28°). Details of each plot are given in Table 1. Significant amount (approx. 15 tonnes/ha/year of Farm-yard manure (FYM), as external input, before showing any crop, for enhancing the crop yield in agricultural
Analysis and results
Data from different experimental plots are analyzed separately in order to understand the effect of different land uses on the variables being studied. Monthly values of runoff, soil erosion and nutrient loss were related amongst themselves and corresponding rainfall values to establish rainfall–runoff-soil and nutrient losses under different land use systems in the studied watershed.
Conclusions
Concurrent data on monthly rainfall, runoff, soil loss and nutrient loss (OM, total P, total N and total K) have been observed from four natural experimental plots having different land covers in Bhetagad watershed of Central Himalaya, India. Analysis of the data revealed that from a given rainfall input, the runoff, soil and nutrient losses were recorded as maximum from pine forest cover. However, per unit loss of OM and nutrients was maximum in the plot having rainfed agriculture as the land
Acknowledgements
The authors are thankful to the Director, G.B. Pant Institute of Himalayan Environment and Development (GBPIHED), Katarmal, Almora (India) for providing necessary facilities. Our sincere thanks are due to Er. K. Kumar for consistent encouragement. We are grateful to the ‘People and Resources Dynamics Project’ (PARDYP) Indian team for their cooperation. Financial assistance from the International Center for Intergraded Mountain Development (ICIMOD), International Development Research Center
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