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All Topics | Topic "Water Balance Check after Calibration (Soil Moisture Method)"
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Author Message
Ms. Beyza Özel

Subject: Water Balance Check after Calibration (Soil Moisture Method)   
Posted: 9/17/2018 Viewed: 4751 times
Hi,

I’m doing some checks after calibrating my watershed. When I look at Land Class Inflows and Outflows for the whole basin in the results view, I want to make sure that streamflow at the outlet of the basin to be equal to the sum of surface runoff, interflow and baseflow. Since those will contribute to the streamflow eventually. But the results don’t match. Relative error is between 0.8-78 %. Also for couple of months, sums of surface flows are much more than modelled streamflow. What do you think is the problem here? I would really appreciate your opinions.

Beyza �zel

Mr. Jack Sieber

Subject: Re: Mass Balance Check after Calibration (Soil Moisture Method)   
Posted: 9/17/2018 Viewed: 4748 times
Hi,

Do you have any reservoirs, that might be adding or removing water to/from streamflow from/to storage? Also, do you have any groundwater nodes that are connected to the river, which might be adding or subtracting water from streamflow? Any evaporation on the river?

Another way to check: You can look at the streamflow in the reach immediately below each catchment inflow node -- the increase in streamflow compared to the streamflow immediately above the catchment inflow node should equal the sum of surface runoff, interflow and baseflow. This will eliminate any effects downstream that might affect streamflow (such as reservoir storage, groundwater interactions or evaporation).

Jack
Ms. Beyza Özel

Subject: Re: Mass Balance Check after Calibration (Soil Moisture Method)   
Posted: 10/11/2018 Viewed: 4704 times
Mr. Sieber,

Thanks to your leading, my problem here was solved. After taking into account all components that contribute to the streamflow, I have established a integrated water balance covering the whole river in the basin. Actually this was what I wanted to do at the first place. When, all inflows and outflows to/from the reaches are taken account, calculated streamflow at the outlet of basin is expected to be equal to the modeled flow. This time, results were matched and then I got %1 of error here.

However, I realized something interesting about catchment simulations. When I go to Catchment-Inflow/Outflows in the results view, inflow and outflow summations (monthly-based) have always an error around %1-2. Actually, there were no such thing like that for the case of other components like groundwater, reservoir or demand site etc. They are all summed up to 0 and water balance seems right. Why do you think is the reason for the case of catchment simulations. Could it be the calibration not being good enough?

Beyza Ozel


Topic "Water Balance Check after Calibration (Soil Moisture Method)"