CIVL3431 – Land Surface Processes and Management
Assignment 2 – Hydrologic Modelling – 20%
This assignment uses a simple lumped rainfall-runoff model, consisting of two storage ‘buckets’ (see Figure 1).
Figure 1. Bucket model
The upper storage represents a small interception canopy (depth = INT), where rainfall is intercepted. When this store is full, any excess moisture (throughfall, TF) enters the soil moisture bucket. Water leaves the soil moisture bucket through two routes – baseflow (Qb) and surface runoff (Qs). Baseflow is calculated as a fixed fraction of the moisture stored (S) in the bucket: Qb = K1.S
Surface runoff is generated as a linear function (Runoff coefficient, RunCo) of the amount of storage (S) above a minimum threshold (Smin) together with TF: Qs=TF.RunCo. When the bucket is full, the amount of TF becoming surface runoff (RunCo = 1), (i.e Qs=0, if S = Smin, Figure 2).
Figure 2. Change of RunCo
ET is calculated from the interception canopy at the potential rate given that there is enough moisture in interception canopy (ET should be PET or whatever in the bucket which is smaller). ET is calculated from the soil store at [(S-Smin)/(SMAX-Smin)]*PET, provided that there is sufficient moisture in the bucket (i.e ET=0, if S =Smin).
Using this model, you will be expected to manually calibrate the four model parameters so that the modelled streamflow series best mimics the observed series for the given calibration data (first 150 time steps), and then use this calibrated model to predict the response of the model to the validation data (last 150 time steps). The observed data used to calibrate the model is in RRdata2018.csv.
Write a report (3-5 pages) that outlines this model, how you calibrated it and how your predictions are affected by your choice of parameters. Your results should include a hydrograph for the full 300 timesteps and a summary of the peak flow and total (cumulative) flow for both the calibration and validation periods. Include a printout of your source code in your report.
Due 17th September 5pm
Students must perform all calculations individually and show all work. Use ONLY the Rainfall Runoff data provided with the assignment (RRdata2018.csv) for model calibration and validation. Identified cases of plagiarism will be dealt with formally through University procedures.