Land use change and hydrologic behavior analysis in the Preto river and Entre Ribeiros creek basins / Mudanças no uso do solo e comportamento hidrológico nas bacias do rio Preto e ribeirão Entre Ribeiros

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The water resources planning and management have the objective to discuss and propose solutions for the watersheds problems looking for the sustainable water use in the urban and rural areas. The relationships between the land use and water resources have been marked by the failure, with environment significant damages, what has transformed in losses for all collectivity. Thus, modifications on stream flows regime can be caused by land use changes, climatic variability, dams construction or irrigation increase. When the land cover is changed for another one, the hydrologic components cycle on watersheds could be modified, changing the stream flow regime. In this way, the Preto river and Entre Ribeiros creek watershed, tributaries of the Paracatu river, drain an area of 14,149km2, which 74.87% (10,621km2) are in the Minas Gerais State, 15.71% (2,212km2) in the Goiás State and 9.42% (1,316km2) in Federal District. Stand out that from 1970 to 2000 the major water consuming agent in the Paracatu river watershed was the irrigation, which had its high participation in 1996 to 93% of the all consumed stream flows. The present work had these objectives: to monitoring the land use change of these basins in the period from 1985 to 2000; to associate the hydrological behavior of the maximum, minimum and mean observed stream flows with the land use variations happened; and to obtain equations for estimate the maximum, minimum and mean stream flows for the fluviometrics stations. This study counted with the analysis of the temporal series of eight fluviometrics stations and eleven pluviometrics stations, in the period from 1985 to 2000, obtaining the maximum, mean, minimum stream flows (Q7, Q90 and Q95) for each year of the selected period, as well as, the average annual rainfall, rainiest month rainfall and driest month rainfall for each fluviometrics stations watershed. The land use change was monitored by 27 images of Landsat TM 5 sensor of the row/path 221/71, 220/71 and 220/72, which were treated by the software SPRING 4.2. The data analysis was done in two parts: qualitative and quantitative analysis. The qualitative data analysis tried to evaluate, through of trend lines, the stream flow, the different land uses and the rainfall behavior along to the chosen period and the association between these variables. It was also obtained the significance of the same ones along the time. Were elaborated diagrams of causal relationships, which they aid in the association among the variables behavior. The quantitative data analysis was accomplished by using the statistical procedures of multiple linear regressions adopting the stream flows as dependent variable and rainfall and the land use as independent variables. Thus, regression equations were adjusted observing the following parameters: determination coefficient (R2) above 0.70, equation significance, independent variables significance, as well as, the coefficients signs. The results showed that the savannah areas decreased significantly in this period mainly on cultivation areas with mean significance of 97.15% and the forest areas grew from pasture areas, significantly to 90.76%. As the qualitative analysis of the association between stream flow and land use variations for the maximum stream flow, the rainiest month rainfall, as well as, the land uses forest and pasture were more explanatory. For the minimum stream flows (Q7, Q90 and Q95) the variables that associate to the same ones were the diary annual mean rainfall, as well as, savannah and cultivation. For the mean stream flow the variables that associate to the same ones were the diary annual mean rainfall, as well as, forest. However, in the quantitative data analysis was observed that the equations for the maximum and mean specific stream flows did not present satisfactory adjustment, except for the minimum stream flows where it was obtained satisfactory R2. However, accomplishing a separately analysis by fluviometrics stations it was obtained satisfactory R2 to four fluviometrics stations to maximum stream flows, six stations to the minimum stream flows Q7, Q90 and Q95 and three stations to the mean stream flows. The variables that presented larger significances were rainiest month rainfall, forest and cultivation for the maximum stream flows; driest month rainfall, savannah, cultivation and forest for the minimum stream flows; and diary annual mean rainfall, forest and cultivation for the mean stream flows.

ASSUNTO(S)

engenharia de agua e solo hydrologic behavior planejamento uso do solo planning comportamento hidrológico water resources recursos hídricos soil use

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