Research On The Effects Of Facility Agriculture On Farmland Drainage Modulus

In order to study the effect of facility agriculture development on drainage modulus of farmland design,a field observation experiment of farmland drainage was carried out in a closed farmland in Xiqing District of Tianjin city.Based on field observation data,construct the infiltration excess–saturation excess vertical coupled runoff model,Sobol' method was used to analysis the sensitivity of the vertical coupled runoff model parameters,and the Shuffled Complex Evolution Algorithm(SCE-UA)with artificial calibration method were both applied to optimize the excess infiltration-excess storage vertical coupled runoff model parameters.Then,the influence of facility agriculture development on drainage modulus of farmland design is discussed by means of simulation analysis.The main results and conclusions of this paper are as follows:(1)Firstly,according to the actual hydrological and meteorological conditions in the study area,the infiltration excess–saturation excess vertical coupled runoff model was established.The water balance conditions and the relative change measure of underground water level and the change measure of soil moisture content were used to evaluate the simulation accuracy of the vertical coupled runoff model and compared with the single excess infiltration runoff model and the single excess storage runoff model for further proving the applicability of the infiltration excess–saturation excess vertical coupled runoff model in this farmland area.The results showed that the relative error of each evaluation index of model accuracy were within 20%,Nsah efficiency coefficient were above 0.6.Compared with the single excess infiltration runoff model and the single excess storage runoff model,the effectiveness of the vertical coupled runoff model were increased by 0.869 and 0.912,respectively.Thus it can be proved the excess infiltration – excess storage vertical coupled runoff model was reasonable and effective in this farmland area.(2)Besides,according to the different recurrence periods of design storm,using the above infiltration excess–saturation excess vertical coupled runoff model to calculate the rainfall yield,then to give the design drainage modulus under different recurrence periods.In the 3 years,5 years,10 years,20 years recurrence periods,the design drainage modulus were increased compared with the original drainage modulus,and the shorter the return period was,the larger the design drainage modulus would increase with the increase value of 16.44%?8.63%?7.50% and 3.77%,respectively.In addition,with the rainfall trend analysis,there were no significant linear change trend between the baseline period and the evaluation period.Therefore,the increase in the proportion of facility agriculture had great influence on the design drainage modulus.(3)To further investigate the effect of facility agriculture on the modulus of farmland drainage,the drainage modulus under different return periods was calculated under the different proportion of facility agriculture occupied and different change proportion of facility agriculture conditions.The results showed that in a short period of recurrence periods,the drainage modulus of facility agriculture area proportion was greatly increased with the enhancing proportion of agricultural facilities.With the comprehensive analysis of the above research results,in recent years,the increasing proportion of agricultural facilities in suburban areas increased year by year,it had great important practical significance to reedit the farmland area drainage handbook for effective control of flood and waterlogging in farmland.