The Influence of the Forest Cover on Hydrology Regulation at Yuracyacu Sub-riverbasin

The investigation evaluated the forest cover in the Yuracyacu Sub-riverbasin and the influence on it’s Hydrological Regulation. For this, 6 Landsat satellite images of the Thematic Mapper (TM) sensor were used for the years 1989, 1995, 2001, 2006, 2008, 2010, on which the respective processing was carried out using CLASlite, generating maps of forest cover for the different years.

The analysis of Hydrological regulation was determined through the study of streamflow regulation, for which models were generated of precipitation, temperature, evapotranspiration, runoff, and thus, by determining the water balance was quantified the water yield.

The loss of forest cover from 1989 - 2010 was 32 km² (3200 Ha) (14% of the Sub-basin), the variation rate was -1,523 km² / year (-152.3 Ha / year). The deforestation rate calculated was -0,012% per year throughout the period of analysis. The validation of the maps, a Global Accuracy overall of 85% and a Kappa Index of 0,65 were obtained indicating the goodness and precision of the classification.

From the analysis of forest cover and water yield, there is an inverse relation, showing that water yield can increase, with the progressive reduction of forest cover in the Yuracyacu Sub-riverbasin, which can trigger problems in the humid season, such as floods and erosion ; negatively affecting the Hydrological Regulation, the greatest increase in water yield is presented for the year 2008, for which a forest cover equal to 116,9 km² was calculated (18% lower compared to the cover of 1989), the water yield being 22l/s/ km², which represents 73,5% more than the average water yield.