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| Some
Effecting Factors on Streamflow in Eastern Watersheds |
| Kittima
Sivaarthitkul , Ratana Jindapol and Rungkarn Krishnamra |
| ABSTRACT |
| In
1992-1993, on studying some effecting factors on streamflow in Eastern
watersheds which divided into 4 basins namely : Mae Nam Prachin Buri
Basin, Mae Nam Bang Pakong Basin, Tonle Sap Basin and East Coast-Gulf
Basin. More than 10 years of historical data of annual flows recorded
from the first year of recording till 1990 are selected. So recorded
mean monthly and mean annual flow of 38 stations which collected by
EGAT are calculated in mean annual flow (Q in mcm.). Ten effecting
factors such as average annual rainfall (R in mm.) during 1952 to
1990 is derived from map prepared by RID in 1992. The others nine
effecting factors are the basin characteristics in term of drainage
area (A in km2.), axial length (L in km.), average width (W in km.),
form factor (F), compactness coefficient (Kc), average inclination
(Si in %) slope of the relief (Sr in m./km.), stream slope (St in
%) and max-min elevation (E in m. and km.). Then simple and multiple linear regression analysis for the relationship between mean annual flow and ten effecting factors on streamflow are analysed by computer. The results are presented as follows; |
| Mae
Nam Prachin Buri Basin (16) For simple linear regression equations which significant in statistic are : 1. Q = - 23.9092 + 0.4570 A (r = 0.9787 , r2 = 0.9579) 2. Q = 7.17 A0.1281 (r = 0.9466 , r2 = 0.8961) 3. Q = - 750.6910 + 62.7790 W (r = 0.9445 , r2 = 0.8920) 4. Q = - 727.6842 + 30.4765 L (r = 0.9009 , r2 = 0.8117) These equations indicate the relationships between mean annual flow (Q) and drainage area (A), average width (W) and axial length (L) are high suitable and precision for estimating mean annual flow in Mae Nam Prachin Buri Basin. For multiple linear regression equation which significant in statistic is : Q = 304.8977 + 0.5369 A - 0.5510 E (R = 0.9862 , R2 = 0.9726) This equation indicates the relationship between mean annual flow (Q) and two factors of drainage area (A) and max-min elevation (E) is high suitable and precision for estimating mean annual flow in Mae Nam Prachin Buri Basin. |
| Mae
Nam Bang Pakong Basin (16) |
| Tonle
Sap Basin (17) For simple linear regression equations which significant in statistic are : Q = 5.29 A0.4651 (r = 0.9175 , r2 = 0.8419) and Q = 14.0775 + 9.7327 W (r = 0.7348 , r2 = 0.5399) The first equation indicates the relationship between mean annual flow (Q) and drainage area (A in term of logarithm). And the second equation indicates the relationship between mean annual flow (Q) and average width (W). Both equation are suitable and precision for estimating mean annual flow in Tonle Sap Basin. |
| East
Coast-Gulf Basin (18) For simple linear regression equations which significant in statistic are : Q = -227.8672+46.8020 W (r = 0.7754 , r2 = 0.6031) and Q = 5.62 A0.5350 (r = 0.7666 , r2 = 0.5877) The first equation indicates the relationship between mean annual flow (Q) and average width (W). And the second equation indicates the relationship between mean annual flow (Q) and drainage area (A). Both equations are suitable for estimating mean annual flow in East Coast-Gulf Basin. For multiple linear regression equation which significant in statistic is: Q= 286.2545 + 0.5422R + 50.0535W - 6.6151Si - 1067.9583Kc (R=0.9933, R2 =0.9866) This equation indicates the relationship between mean annual flow (Q) and four factors of average annual rainfall (R), average width (W), average inclination (Si) and compactness coefficient (Kc). And the equation is high suitable and precision for estimating mean annual flow in East Coast-Gulf Basin. |
| Keywords : Streamflow, Eastern Watersheds |