Modelling of the hydrological parameters in the experimental and representative Ciurea-Tinoasa hydrographical basin

Abstract

The overall goal of the paper is to find the impact of the overland flow and topography on groundwater in the Experimental and Representative Ciurea-Tinoasa hydrographical basin using the MIKE 11 software developed by Danish Hydraulic Institute. The Ciurea-Tinoasa watershed consists of 4 subcatchments but, due to the small area, all of them were analyzed as a unitary one. This basin represents a relevant source of hydrological and meteorological information for Moldova area due to the fact that it is endowed with suitable equipment meant to monitor the main parameters needed to make a reliable model analysis.
Using hydrological time series consisting of daily values of rainfall, evaporation and observed discharge, the watershed was modelled by Rainfall Runoff/NAM (Nedbør-Afstrømnings-Model) module and connected to the HD network, which was modelled by the HD model of the same software, in a suitable way. The model was calibrated using the data recorded for a time period of 3 years and validated by other additional 3 years of available data.
Regarding the NAM parameters, only nine of them representing the Surface-zone, Root-zone and the Groundwater storages where used, while the snow melt and irrigation were not included. These parameters were calibrated by the automatic calibration routine which is based on a multi-objective optimization strategy in which the four different calibration objectives can be optimized simultaneously: (1) Agreement between the average simulated and the observed catchment runoff: overall volume error; (2) Overall agreement of the shape of the hydrograph: overall root mean square error (RMSE); (3) Agreement of peak flows: average RMSE of peak flow events; (4) Agreement of low flows: average RMSE of low flow events. After the parameters were calibrated twice, the results were satisfactory, with a good concordance between the observed discharged and the simulated one.
The groundwater response to overland flow and topography is obtained due to coupling these two models (HD and RR). The result includes estimated parameters such as infiltration, ground water depth, recharge, capillary flux and runoff. Taking in consideration the conceptualization of the flow system and the accuracy required in the basin which was analyzed, the choice of the methods that we used in order to estimate reliably the recharge of the groundwater is satisfactory. The methodology used allows a rapid and comprehensive determination of the recharge, which is important for estimating the available water resources and groundwater vulnerability.