The prediction of hydrological responses in a microbasin from different soil uses is of fundamental importance to develop actions to minimize environmental impacts. This work aimed to develop and to apply hydrological modeling for predicting surface runoff and peak discharge in experimental tropical ephemeral watershed occupied by eucalyptus and grasses, creating different soil use scenarios. Hydrological monitoring was performed between November/2002 and April/2003, using, respectively, gauge and climatologically stations. Soil moisture was monitored every 2 days, at 3 depths (20, 50 and 80 cm), at 8 distributed spatial points in the grass area and 4 points in the eucalyptus area. The modeling has presented a high precision, thereby showing to be very effective for application for the proposed goals. In scenarios which eucalyptus area is larger than the grass area there will be surface runoff reduction of up to 29%, when the microbasin would be occupied by 80% of this vegetable cover. Also, a substantial reduction in peak discharge was verified. The modeling showed itself to be precise and effective in relation to the proposed prediction objectives in different scenarios of soil use and ocupation. It was verified that, if the microbasin was occupied by 80% eucalyptus, there would be a reduction in surface runoff of 29%, and furthermore, a substantial reduction in peak discharge. Also verified was that soil water is fundamental in the process, especially for small flows, at the beginning and end of the rainy period and after short dry seasons and that, for higher flows the rainfall characteristics are determinant.
hydrology; soil use; soil moisture
