Spatiotemporal analysis of the effects of forest covers on stream water quality in Western Ghats of peninsular India

- Studies the effect of mixed forest cover on stream water quality in tropics.
- Quantifies the impact of forest cover on important water quality parameters.
- Observes contrasting response of the old and disturbed forests on water quality.
- Observes tradeoff between provisioning services and hydrological services of forests.

SummaryThe hydrological research has largely concentrated on two extremes - undisturbed forest cover versus cleared forest land, whereas most tropical forest areas are now a mix of secondary vegetation, and old forest interspersed with patches cleared for agriculture or other non-forest use (Bruijnzeel, 2004; Giambelluca, 2002). For this reason, research on spatiotemporal variations in the effects of a mix of primary forest, mature secondary forests and disturbed forests on stream water quality was conducted in four watersheds in the Western Ghats of peninsular India. The study indicated that every one percent decrease in the forest cover (all lands with tree cover of canopy density of 10% and above when projected vertically on the horizontal ground with minimum areal extent of one ha) increases turbidity, total suspended solids (TSS) and Escherichia coli by 8.41%, 4.17% and 3.91%, respectively as also decreases calcium hardness by 0.49%. However, when the forest cover was segregated into old forests (primary forest, mature secondary forest and undisturbed mature plantations) and, open and disturbed forests the old forests were observed to significantly improve (p < 0.05) most water quality parameters. In contrast the open and disturbed forests were observed to deteriorate the observed water quality parameters except for turbidity and TSS. The magnitudes of regression coefficients indicated that the old forests were 2.2 and 2.74 times more effective than the disturbed forests in reducing turbidity and TSS, respectively. Tradeoffs between the provisioning services and water quality improvement services of the forest were apparent.