Usually, in order to check the consistency of rainfall or streamflow data, Double Mass Curve method compares dataset from one gauge to the average value of several dataset from the nearby gauges, which are on different stream but still in the same watershed area. Now, I want to check the consistency of two streamgages on the same river, one gauge is on the middle stream, and another one is on the downstream area. Considering the various factors that would happen between those gauges, is it applicable?
I would think useful comparison, possibly help recover some estimates of missing data, or help identify instances of difference that could be looked into, such as storm differences. I have compared two stations in same drainage with streamflow data collected every 15 minutes on a plot, and this would not work, as there is a variable time delay in response of upper site and lower site, base in part due to discharge rate (e.g., mean velocity) and storm differences in timing and intensity, elevation differences, etc. Even working with daily data, this time of concentration difference can show up as some days storm reaches upper gauge near end of day, but lower site is not responding until next day. If working with monthly or annual data, the effect of the time of concentration difference could theoretically make a difference, but when checking records, one can more easily find conditions where a single event caused one to respond but the other could not due to timing. In areas with localized thunderstorms, you may find instances where the two stations are responding differently. In my experience with upper and lower Chattooga River, I was able to develop an exponential flow relationship between two stations, with some adjustment in time of concentration between two sites depending on discharge values. The upper site had more rainfall, and on average, it’s upper watershed storm peaks were 48% of the much larger downstream site, with some substantial scatter on specific storms.
I would think useful comparison, possibly help recover some estimates of missing data, or help identify instances of difference that could be looked into, such as storm differences. I have compared two stations in same drainage with streamflow data collected every 15 minutes on a plot, and this would not work, as there is a variable time delay in response of upper site and lower site, base in part due to discharge rate (e.g., mean velocity) and storm differences in timing and intensity, elevation differences, etc. Even working with daily data, this time of concentration difference can show up as some days storm reaches upper gauge near end of day, but lower site is not responding until next day. If working with monthly or annual data, the effect of the time of concentration difference could theoretically make a difference, but when checking records, one can more easily find conditions where a single event caused one to respond but the other could not due to timing. In areas with localized thunderstorms, you may find instances where the two stations are responding differently. In my experience with upper and lower Chattooga River, I was able to develop an exponential flow relationship between two stations, with some adjustment in time of concentration between two sites depending on discharge values. The upper site had more rainfall, and on average, it’s upper watershed storm peaks were 48% of the much larger downstream site, with some substantial scatter on specific storms.
You may find different values as a function of many variables, such as gradient, river length, stream shape, rainfall, geology, etc ...
Hanson's response covers the situation well.
Just try plotting the two gage data's against each other, for various time-averaging periods, and possibly also trying a few time delay periods. You may find the correlations can be weak or with big outliers for short averaging periods (e.g., less than a day), but very strong for long averaging periods (e.g., more than a week). I found very strong correlations for each of a couple of streams (each with 2 gages) in a mountain basin in California USA (the Tahoe Basin) for monthly and annual averaging periods (I did not look at storm-scale or other shorter averaging periods).
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