Hi, looking to get some assistance

[ASCivil72]

Hi, looking to get some assistance in computing the water soil storage capacity in a soil horizon next to a ditch. We will be filling the ditch and the loss in water capacity will need to be compensated for according to the local drainage district. I must confess haven't done this type of problem since college - any help would be appreciated! I know the parameters to get are:
1. water level in the ditch
2. normal groundwater level in the area
3. soil conductivity of the native soil
4. Soil storage or CN value of soil

What else am I missing? What is the algorithm(s) from here?

 

[msquared48]

Considering the voids in the soil, if the water is not flowing through the ditch as in a stream situation, the volume of storage to replace would be about 70 % of the volume of the ditch.

Mike McCann, PE, SE (WA)