Morfologia e aspectos hidrológicos da microbacia Rua Nova, Viçosa-MG, para fins de manejo

Abstract

The objective of the present work was to characterize some physical and hydrological parameters of a small watershed, so that the information achieved may contribute for the plans of soil and water management and conservation in the zona da mata region, in minas gerais, in a way to provide water storage and supply. It is important due to the conservation status of the hydrographic watersheds of the region, especially the one of the são bartolomeu river, which is faulty, thus hindering the water provisioning. It was made, in the microbasin of rua nova, Viçosa, Mg, an evaluation of the physiographic indices, soil distribution in the landscape and its physical-chemical characteristics, as well as of the rainfall distribution and its effect on the water discharge, focusing the mangement for water infiltration and storage. The small watershed of rua nova turned out to be a very valuable area for planning and studying environmental recovery morphological due to its size, the importance of the region and the easy control of the anthropics interference. It was possible to verify that the physiography, combined to the morphology and soil use, influences the runnof. It has a prolonged shape and is not easily subject to floods. In spite of its rich drainage, the aquifers are not properly supplied, since not all of the streamflow presented a perennial flux. The average altitude of the area was 763,23m and the average declivity was 24,23o, due to the geographic features of the region, which interfere in agriculture. Besides, the declivity is also associated to the increase of the runnof flux velocity on the top of. The hills and on the steep slopes, the scarce green cover resulting from the soil chemical poverty and intense pasturing contribute to decrease the soil resistance to erosion. In the concave portion of the landscape and on the bottom of the valley, the kind of soil argissolo prevailed. In pasturing, the the convex and cambissolos steep prevailed. Areas used however, in for that very relief portion which was covered with brush-wood, the prevailing class was latossólica. The top of the hill portion covered with woods presented characteristics of red-yellow-latossolo and, in that same portion covered with pasture, the soil presented characteristics of red-latossolo. The fraction silte presented a higher e level in the steep portions covered with pasture, which indicates the need of soil protection in those environments, due to instability and lack of resistance to erosion. The pasture pressure is also giving more density to horizons, which hinders water infiltration in the soil profile. In general, the soils presented low fertility, mainly the soils of the higher areas. The volume of rain collected in the experimental period was 946, 7mm, with distinct dry and rainy periods and the occurrence of a water discharge. In the rainy periods, the superficial flux was greater, due to the reduced infiltration capacity caused by the high level of humidity in the soil and the poor soil conservation, which do not favor the water infiltration in the soil.