Flow-duration curves

To gain a better understanding of the annual and seasonal effects of the two future climate scenarios considered in the present analysis, three types of monthly flow duration curves are computed one with all the monthly streamflows (left column), another only with the winter (DJF) monthly streamflows (centre column), and final one with the summer (JJA) streamflows only (right column). 

Monthly Flow Duration Curve on Q063, Subb=79... 

WINTER (DJF) Flow Duration Curve on Q071, Subb=90... 

WINTER (DJF) Flow Duration Curve on Q093, Subb=115 SUMMER (JJA) Flow Duration Curve on Q093, Subb=115... 

Monthly Flow Duration Curve inflow to E801, Subb=57... 

Fig. 14 Monthly flow duration curves for the subcatchments 057, 079, 090 and 115. Black lines refer to the flow duration curves obtained by considering the observed values during the control period 1961-1990, while the blue and red lines refer to the streamflows derived from the two RCMs HIRHAM H and RCAO E, respectively. The left column represent the flow duration curves computed with all the monthly values during the period 2071-2100 the central column was computed with the monthly values belonging to the winter season (DJF) and the right column represent the flow duration curve computed with the monthly values belonging to the summer season (JJA). Note that vertical scales are different...

Vogel R, Fennessey NM (1994) Flow duration curves I A new interpretation and confidence intervals. ASCE, J Water Resour Plan Manage 120(4) 485-504... 

One useful technique that developed in the twentieth century was to use the low-flow and high-flow ends of flow-duration curves to provide useful information about the hydrogeologic characteristics of... 

The second category, time-dependent behaviour, is common but difficult to deal with. The best known type is the thixotropic fluid, the characteristic of which is that when sheared at a constant rate (or at a constant shear stress) the apparent viscosity decreases with the duration of shearing. Figure 1.21 shows the type of flow curve that is found. The apparent viscosity continues to fall during shearing so that if measurements are made for a series of increasing shear rates and then the series is reversed, a hysteresis loop is observed. On repeating the measurements, similar behaviour is seen but at lower values of shear stress because the apparent viscosity continues to fall. 

As above, assuming a constant average inflation rate, which is then used to calculate the value of the bond s coupon and redemption payments. The duration of the cash flow is then calculated by observing the effect of a parallel shift in the zero-coupon yield curve. By assuming a constant inflation rate and constant increase in the cash flow stream, a further assumption is made that the parallel shift in the yield curve is as a result of changes in real yields, not because of changes in inflation expectations. Therefore, this duration measure becomes in effect a real yield duration ... 

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