Xiyun Jiao

Urban Weather Data to Estimate Reference Evapotranspiration for Rural Irrigation Management

AbstractWeather data measured in urban areas are generally more easily available than those in rural areas. If the urban weather data are used to calculate the reference crop evapotranspiration (ET0) for rural irrigation management or spatial and temporal trend analysis, the results may be biased because of the differences in weather variables. We collected daily data for mean, maximum, and minimum temperatures; relative humidity; average wind speed; and sunshine duration from two stations: Kaifeng Station in the City of Kaifeng and Huibei Station in the nearby irrigation scheme for 1984–2009. ET0 for both stations were calculated using the FAO-56 Penman-Monteith method and then compared. The results indicated that the difference in daily ET0 was remarkable [with relative error (RE) of 52.6%], the difference between monthly average ET0 increased gradually during the last three decades and the temporal trends in annual average daily ET0 were opposite. There were significant differences in ETC (with RE of 3...

Forecasting daily reference evapotranspiration using the Blaney–Criddle model and temperature forecasts

ABSTRACT Accurate daily reference evapotranspiration (ETo) forecast is essential for real-time irrigation scheduling. An attempt was made to forecast ETo using the Blaney–Criddle (BC) model and temperature forecasts in this study. Daily meteorological data for the period 2000–2014 at five stations in East China were collected to calibrate and validate the BC model against the FAO56 Penman–Monteith (FAO56-PM) model. Temperature forecasts up to 7 days’ lead time for 2012–2014 were input to the calibrated BC model to forecast ETo. It is found that the performance of the BC model for ETo forecast is further improved at all stations after monthly calibration. Average accuracy of forecasted ETo (error within 1.5 mm d−1) ranged from 82.7% to 89.3%, average values of mean absolute error (MAE) varied between 0.73 and 0.82 mm d−1, average values of root mean square error (RMSE) ranged from 0.95 to 1.08 mm d−1, and average values of the correlation coefficient (R) and concordance index (d) were more than 0.75 and 0.89, respectively. Furthermore, the error in ETo forecast caused by error in temperature forecast is acceptable. The encouraging results indicate that the proposed method can be an alternative and effective solution for forecasting daily ETo in East China.

Irrigation Management Using Different Irrigation Scheduling Techniques in Blocked-end Furrows

Surface irrigation under different irrigation techniques is evaluated in this research, based on water applying method, water infiltration depth, and irrigation water use efficiency. For that purpose, field experiments were conducted using cotton grown in silt loam soil at Wuqiao Eco-Agricultural Experimental Station in 2015 season. To evaluate the infiltration and distribution under conventional continuous inflow in comparison to increased discharge and decreased discharge irrigation in blockedend furrows, nine irrigation treatments were applied. They are known as continuous flow irrigation (CFI), decreased discharge irrigation (DDI) and increased discharge irrigation (IDI). In DDI and IDI irrigation treatments, the inflow should be varied before the completion of the advance phase and cut off time in all treatments when the advance wave reaches the end of the field. The infiltration depth in cm was functioned to opportunity time (  ) in minute for the double ring infiltrometer as: 381 . 0 51 . 0   Z .The average application efficiency of DDI irrigation is higher than that of CFI and IDI irrigation treatments. Decreased discharge in DDI irrigation treatment when the position of the advancing wave front reaches 0.75 of the furrow’s length can potentially save water and irrigation time compared with other irrigation treatments.