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.
Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar2Environmental Modelling A Simple Hydrologic Model Hardisty, et al Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
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 Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley.
Geog 409: Advanced Spatial Analysis & Modelling © J.M. Piwowar10Environmental Modelling Hardisty, et al Computerised Environmental Modelling: A Practical Introduction Using Excel. Chichester: Wiley. The “Catchwater” Drainage Basin