So far, I could not find a single paired-watershed experimental stream flow data on a tropical native forest. FAO & CIFOR (2005) make generalized statements like “…Considerable quantities of rainfall (up to 35 per cent) are commonly intercepted by the canopies of tropical forests and evaporated back into the atmosphere without contributing to soil water reserves…” but they do not present data on native tropical forests. Pine and Eucalyptus forests tend to trap rainwater to the levels mentioned by FAO, but the common sense tells us that the same is not true for native forests. My suspicion is, given the high uncertainty in measuring stream discharge (up to 43% - Baldassare and Montanari (2009)), we may not be able to detect any watershed cover effects on the stream flow, even in the case of exotic trees, worse for native forests. When science is not capable of producing data, why can’t we accept the ‘common sense’ with humility, instead of labeling that as ‘popular myth’?
FAO & CIFOR (2005) “Forests and floods: Drowning in fiction or thriving on facts?”, Center for International Forestry Research, Indonesia and FAO Regional office for Asia and Pacific, Thailand.
Baldassarre, G. Di and A. Montanari (2009) “Uncertainty in river discharge observations: a quantitative analysis”, Hydrol. Earth Syst. Sci., 13, 913–921, www.hydrol-earth-syst-sci.net/13/913/2009/
We have done some studies in India on this, but the comparison between exotic and native cover was not specifically studied, although new and non-native species were introduced in forest watersheds. Introduction of grass cover certainly improved the stream flow and reduced soil erosion substantially, especially in upper reaches of the watershed where structures are difficult to have.
It depends on factors, such as, forest (species) composition and diversity, soil type, slope, soil and water conservation practices, planting pattern of introduced species in case of exotic species, etc. Certainly, introduction of grasses as under story in forests reduce run off and soil loss and enhances stream flow. More over, human interventions/encroachments may accelerate erosion, run off and soil loss.
You may refer to:
1. Palsaniya, D. R., Singh, R., Yadav, R. S., Tewari, R. K. and Dhyani, S. K. 2011. Now it is water all the way in Garhkundar – Dabar watershed of drought prone semi arid Bundelkhand, India. Current Science, 100(9): 1287-88.
2. Palsaniya, D.R., Tewari, R.K., Singh, Ramesh, Yadav, R.S., and Dhyani, S.K. 2010. Farmer – agroforestry land use adoption interface in degraded agroecosystem of Bundelkhand region, India. Range Management and Agroforestry. 31(1): 11-19.
3. Singh, Ramesh, Yadav, R.S., Tewari, R.K., Palsaniya, D.R., Kumar, R.V., Dwivedi, R.P., Venkatesh A., Rizvi, R.H. and Dhyani, S.K. 2010. Impact of watershed management on controlling runoff and soil loss in Garhkundar_Dabar watershed. Range Management and Agroforestry, Symposium issue (B): 233-234.
4. Palsaniya, D. R., Singh, R., Tewari, R. K., Yadav, R. S. and Dhyani, S. K. 2012. Integrated watershed management for natural resource conservation and livelihood security in Semi Arid Tropics of India. Indian J. Agricultural Sciences 82 (3): 241-7, March 2012.
Thanks. I read with interest the results of conservation measures. Unfortunately, I could not comprehend how they were planned and to what extent the people 'owned' the actions. Because I am writing about what people could do to help watersheds. could you help with some sources?
It depends on various environmental and biophysical parameters. Baseflow as well as other hydrological factors can be affected by land cover, slope, aspect, infiltration and so on. I think To answer this question, you should review the articles by which consider sensitivity analysis over precipitation-runoff models over the region.
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