The study is aimed at derivation of a spatially Distributed Unit Hydrograph for Temur watershed using Geographical Information Systems (GIS) based Distributed Unit Hydrograph Approach. The method for Distributed Unit Hydrograph computation allows for spatial non-uniformity of excess rainfall and is based on the time-area method derived using GIS.
The GIS allows development of a watershed’s channel network for calculation of realistic travel times. It handles the distributed excess rainfall in calculating local surface runoff rates as inputs for channel flow and it compiles the time-area diagram from which Distributed Unit Hydrograph is derived.
Simulation results show that the errors between observed and simulated peak discharge are from -5.8 % to 22.1 %, which is well within acceptable limits for designing small structures on the stream. However, the errors between observed and simulated time to peak is large compared to errors in peak discharge simulations.
Graphical comparison of observed and simulated discharge shows that the rising limb of computed hydrograph matches well with the rising limb of observed hydrograph in all cases. However, the recession shape of observed and simulated hydrograph does not match very well. This could be attributed to the fact that a very simple method for velocity simulation was used and no calibration of parameters has been performed. Also a pure translation method has been used in the study, which could be responsible for lack of agreement in shape of hydrograph.
The topographic maps of the catchment indicate mild slopes in most of the area and there is a likelihood of storage effect due to this. The study indicates that the method works well for simulation of peak discharge and would need further refinement for overall shape and time of peak discharge simulation. It is therefore appropriate to simulate this catchment with the model, which takes both translation and storage effects into consideration for further study.
Download the report here:
/articles/watershed-modeling-gis-based-distributed-unit-hydrograph-approach-research-report-national