1. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar1Environmental Modelling A Drainage Basin Modelling Example Object:  To determine the channel discharge of a small drainage basin for a given rainfall.

2. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar2Environmental Modelling A Simple Hydrologic Model Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

3. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar3Environmental Modelling Rainfall  Precipitation less evaporation losses.  Assume rainfall falls evenly over the basin.  R = rainfall * surface area Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

4. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar4Environmental Modelling Surface Storage  The amount of rainfall that is detained on the surface.  Assumptions:  There is some pre-existing surface storage  One-half of rainfall is retained in surface storage.  S = S + 0.5*R Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

5. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar5Environmental Modelling Surface-Channel Discharge  The proportion of water in Surface Storage that immediately runs-off.  Q SC = surface storage * constant 1  Initial Assumption: constant 1 = 0.9 Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

6. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar6Environmental Modelling Surface-Ground Discharge  The proportion of water in Surface Storage that percolates into the ground.  Q SG = surface storage * constant 2  Initial Assumption: constant 2 = 0.6 Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

7. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar7Environmental Modelling Groundwater Storage  The amount of water in the unsaturated soil layers and in the saturated zone below the water table.  Assumptions:  There is some pre-existing groundwater storage  One-half of percolating rainfall is retained in groundwater storage.  G = G + 0.5*Q SG Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

8. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar8Environmental Modelling Ground-Channel Discharge  The proportion of water in Ground Storage that seeps back to the surface.  S GC = ground storage * constant 3  Initial Assumption: constant 3 = 0.3 Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

9. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar9Environmental Modelling Channel Discharge  The sum of the water run-offs from the surface and from the ground. Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.

10. Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar10Environmental Modelling Hardisty, et al. 1993. Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley. The “Catchwater” Drainage Basin