DISCHARGE AND HYDROLOGICAL SIMILARITY OF DRAINAGE BASINS
| Autor: | Toshie Nishizawa |
|---|---|
| Rok vydání: | 1970 |
| Předmět: | |
| Zdroj: | Geographical Review of Japan. 43:527-534 |
| ISSN: | 2185-1719 0016-7444 |
| Popis: | Discharge is closely related not only to geological characteristics and vegetation of a basin but also depends upon geomorphic factors such as drainage area, stream length, stream number, stream order, basin shape, and ground slope. Hack plotted average discharge on a logarithmic graph for all gaging stations in the Pot-omac River basin and fitted a regression line with an exponent of 1.0. In general, an empirical equation relating stream discharge (Q) to basin area has shown to be Q=jAm……………………………………………………………… (1) where j and in are constants. The exponent in generally falls in the range from 0.5 to 1.0. For instance, in the case of annual mean discharge on the Potomac River basin, in is 1.0; it is 0.70 for flood discharge on twelve streams of New Mexico. On the other hand, the specific discharge of annual mean decreases exponentially with an increase of drainage area in Japanese river basins. This result agrees with the case of m≠1.0 in equation (1) and is different from the example of the Potomac River basin shown by Hack. It is supposed that non-linear relation of specific discharge to basin area is caused not only by areal localization of precipitation but also depends on irregularity of stream network. The purpose of this paper is to show the relationship between discharge and geomorphic characters of a basin such as stream order, stream length, and stream number, in terms of the concept of similarity. In general, assuming that the discharge is constant during the period of observation, the discharge (Qu) of drainage with order U is expressed as follows:_??_.……………………………………………………………… (2) where u is the stream order defined by 5trahler's ordering using a map on a scale of 1 50, 000. _??_u and Nu are mean length and number of stream with order u respectively. qGu and qsu are mean discharge of stream of order zc due to ground and surface water flows respecti-vely and these have the dimension of (m2/sec). Using Horton's first and second laws: _??_u+1/_??_u=γl, Nu+1/Nu=γb and, further assuming that the following ratios are the same in the whole basin :_??_ the equation (1) is transformed as follows: _??_+………………+_??_………………(3) Moreover, in order to generalize, if we substitute the characteristics of u-th order, l1, N1, and qau, for l1, N1, and qG1, in equation (3), the dischorge is rewritten as follows: _??_………………………………………………………………… (4) _??_ where _??_u is a proportional constant. This theory is supported by the observations of discharge carried out on two basins, the Kanna River basin and the Koshin River basin. The discharge was measured by the floating method at seven points along the Kanna River on May 2021, 1967 and at seven points along the Koshin River on June 16, 1969. As the weather had no precipitation during the observations, the discussions in this paper are the case of without the surface water flow in equation (4). Figs. 2 and 4 show the relation discharge to (_??_uNu) and the slopes of regr-ession lines are 1.0 in all cases. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|