An
investigation on the effect of drainage morphology and deforestation on
streamflow characteristics of Mun river basin were utilize historical
data of annual streamflow and rainfall during 1972 to 1991 by Royal
Irrigation Department, forest area by the Royal Forest Department and
soil series by Department of Land Development were formulated.
Streamflow
varied directly with annual rainfall (R), drainage area (A), soil
moisture freely drain by gravity (G), stream density (SD) and drainage
density (DD) but varied inversely with forest area (F), average
inclination (I), compactness coefficient and relief ratio, However,
comparative regression by linear and curvilinear found that curvilinear
was better than linear, the model was
Q =
6.97 * 10-7 * R1.7931 * A0.8882 * RE0.5914
* DD-0.2242 * SD0.4080 Kc-0.3605 *
G0.4133 * F-0.0154 ;
r2 = 0.7619, F-ratio = 76.38**
This
model indicated that when forest area decrease for every 10% could
probably increase streamflow at about 622 m3/km2.
And found that the ratio of streamflow in dry season to wet season was
about 0.42 for the first ten-year (1972-1981) and 0.30 for the second
ten-year(1982-1991). In case of without upstream reservoirs, the ratio
was about 0.009-0.2 for the first ten-years and 0.007-0.14 for the
second ten-year. Moreover, streamflow quantity trend to increase in wet
period and decrease in dry period during the second ten-year. This
phenomena thus implies that without intensive watershed rehabilitation
in the future, flood and water shortage would become a harsh problem.
