Water balance for the Ji-Paraná Basin using remote sensing and GIS
Daniel
de Castro
Victoria, LGTI - CENA/USP, dvictori@cena.usp.br
(Presenting)
Maria Victoria
Ramos
Ballester, LGTI - CENA/USP, vicky@cena.usp.br
Antonio
Roberto
Pereira, Dep. Ciências Exatas - ESALQ/USP, arpereir@esalq.usp.br
Luiz
Antonio
Martinelli, Lab. Ecologia Isotópica - CENA/USP, zebu@cena.usp.br
Jeffrey
E.
Richey, School of Oceanography, University of Washington, jrichey@u.washington.edu
Reynaldo
Luiz
Victória, LGTI - CENA/USP, reyna@cena.usp.br
The growing change in landuse and cover that has been happening in the state of Rondônia, especially in the Ji-Paraná basin, could result in changes in various ecosystem components, including the water balance. The Thornthwaite-Mather water balance model was inserted into a Geographic Information System in order to estimate the monthly water balance at the whole basin. The input parameters, for the years 1995 and 1996, were: Mean monthly temperature images, composed by daily AVHRR images, pre-processed by an automatic cloud detection algorithm and used to estimate potential evapotranspiration; mean monthly precipitation, interpolated from 31 stations inside and near the study area; soil texture, derived from geostatistical analysis of 756 soil profiles and root depth, estimated from the landcover map. The results show that the model is temporal and spatially coherent, predicting water deficit during the dry periods of the region and also, areas inside the basin with water deficit or surplus are coincident with the precipitation distribution. However, the model underestimated the annual potential evapotranspiration, estimated at 1050 mm, and real evapotranspiration (864 mm), both values less than the real evapotranspiration obtained by water mass balance for the same period (1276 mm). Future adjustments to the model have yet to be made, such as an increase in the rooting depth and also some enhancements in the monthly temperature composite images, used in the potential evapotranspiration estimate.