4.6 Impact on water availability and withdrawal pattern by Hydrographs shifting method
The relative shape and trend of hydrograph of different year are useful to analyze water availability and withdrawal pattern of certain river. The early shift of the hydrographs seems to be clear in snow-fed river basins like the Kali Gandaki (Figure 4.18) and also in Bagmati rain-fed rivers originating in the midland (Figure 4.19).
Figure 4.18: Shifting hydrograph in the Kali Gandaki River (1964-1995)
4.6.1 Result and discussion: The climate change effect is clearly visible from the analyzed hydrograph of Kali Gandaki River (One of the major River of Central Nepal) which shows that in the snow-fed river, water available days on the river was in decreasing…show more content… This also implies that numbers of rainy days were decreasing and intensity and frequency of rainfall is increasing while total runoff is in increasing trend. Very sharp pointed hydrograph in the year 2000 explains that water available in the river is for short period with discharge 600m3/s. In contrast, during the year 1965, the discharge water was available for the longer period (blunt shape of hydrograph) and the discharge rate was…show more content… The increasing trend of the flooding in the river may be changes in the precipitation pattern in the recent years. In short, number of frequency and duration of flooding is an increasing trend and this kind of flooding due to climate-induced water might impact greatly in the socioeconomic development of Nepal by means of money and life which is also described by the figure 4.22.
Figure 4.22: Flood and landslide disasters in Nepal due to induced climate change (Khanal, 2005)
4.8 Impacts on Droughts
Dry season flow (January-April) is the best suitable time for the drought study. However, in the drought analysis 120 days daily record of flow in the Kali Gandaki river have analyzed and below the mean (μ) and standard deviation (σ) level of flow in the river has been indicated to the drought day which named as threshold band (μ−σ) which is shown in the figure
