Storm hydrograph

Figure 3.4 Hypothetical storm hydrograph for a period of 2 days (with evenly distributed precipitation) showing how changes in overland flow are responsive to precipitation and correlate well with changes in total stream flow. Conversely, groundwater inputs (baseflow) remain essentially constant during this period. (Modified from Fetter, 2001.)...

Ogunkoya O. O. and Jenkins A. (1993) Analysis of storm hydrograph and flow pathways using a three-component hydrograph separation model. J. Hydrol. 142, 71-88. 

FIGURE 6 Characteristic storm hydrograph for a drainage basin and actual flow records for the Portage River at Woodville, Sandusky County, OH for the month of April, 1997. 

Isotope hydrograph separation apportions storm and snowmelt hydrographs into contributing components based on the distinctive isotopic signamres carried by the old and new water components. Hence, the method allows the calculation of the relative contributions of new precipitation and older groundwater to stream flow. A major limitation of the tracer method is that we cannot directly determine how the water reaches the stream (i.e., geographic source of the... 

Two-component mixing models. Isotope hydrograph separation normally involves a two-component mixing model for the stream. The model assumes that water in the stream at any time during storm or snowmelt runoff is a mixture of two components new water and old water. 

Stable isotopes such as and are an improved alternative to traditional nonconservative chemical tracers, because waters are often uniquely labeled by their isotopic compositions (Sklash and Farvolden, 1979 McDonnell and Kendall, 1992), often allowing the separation of waters from different sources (e.g., new rain versus old pre-storm water). However, smdies have shown that flow paths cannot be identified to a high degree of certainty using 5 0 or data and simple hydrograph separation techniques, because waters within the same flow path can be derived from several different sources (Ogunkoya and Jenkins, 1991). Thus, a number of plausible mnofif mechanisms can be consistent with the isotope data. The need to incorporate flow path dynamics is recognized as... 

Hinton M. J., Schiff S. L., and English M. C. (1994) Examining the contributions of glacial till water to storm runoff using two-and three-component hydrograph separations. Water Resour. Res. 30, 983-993. 

McDonnellJ. J., BonellM., Stewart M. K., andPearceA. J. (1990) Deuterium variations in storm rainfall implications for stream hydrograph separations. Water Resour. Res. 26,455-458. 

Al T. A. and Blowes D. W. (1996) Storm-water hydrograph separation of run off from a mine-tailings impoundment formed by thickened tailings discharge at Kidd Creek, Timmins, Ontario. J. Hydrol. 180, 55-78. 

The response of Q to the storm events is difficult to ascertain, as it was obscured by the immediate and dramatic increase caused by removal of the dam gates after the storm events (Figure 7). However, it is clear that the spring hydrographs would have peaked at some time less than 26 hours after rainfall. 

Storm drainage systems can also affect stream flow, as runoff is deliberately directed into nearby streams. This rapid exiting of water from the increased impervious area can quickly reduce the Is time between precipitation input and flood runoff. The resultant increase in the stream hydrograph invariably gives rise to peak discharge flows that result in local and regional flooding. 

In open coastal areas, the rise in water level due to a surge is usually represented by a single peak surge generated by a wind storm. On top of this, the effect of waves should be determined. In an enclosed or semi-enclosed body of water such as a lake or harbour a storm can cause the oscillation of the water surface which can result in a multipeak surge hydrograph. 

Summary tables and plots of the total storm surge hydrographs for specified locations. 

In some cases, such as for very small basins, making allowance for the antecedent storm may not be necessary because the hydrograph will have reached the base flow rate in the interval preceding the storm. In such cases a conservatively high base flow rate and soil moisture level should be used instead of making allowance for the antecedent storm. A more conservative approach is to use values for the antecedent storm together with the median soil moisture level and the mean base flow rate as the initial conditions. 

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