Abstract
Accurate quantification of evaporation loss from irrigation canals at an irrigation district scale is very useful for developing efficient irrigation strategies, particularly in water-deficient regions. The double-deck surface air layer (DSAL) model, a new aerodynamic method proposed by Kobayashi et al. (2013), is used for estimating the evaporation loss from a running water surface in irrigation canals. In this study, based on the long-term meteorological measurements made at automatic weather stations in 2013 and the field experiment conducted at - midstream areas of the Heihe River Basin (HRB), northwestern China, the DSAL model was applied to estimate the long-term evaporation loss from irrigation canals, which was the remarkable highlight of the study. The results showed that the rate of evaporation from irrigation canals exhibited a concave-up trend for the period from June to September, with higher values in June and September (20 to 50 mm day−1) and lower values in July and August (around 10 mm day−1). During the four months, for the Yingke and Daman irrigation districts in the Zhangye Oasis, the total water losses from irrigation canals due to evaporation were approximately 23.9 × 105 m3 and 36.6 × 105 m3, or 3.2% and 4.8% of the total amount of irrigation water, respectively. Results of the study are not only important for improving the irrigation water use efficiency, but also are beneficial to develop sustainable water resource management in the midstream areas of the HRB.
Highlights
Many inland river basins in arid and semiarid regions are suffering from the collapse of water resource system and ecology, because of water scarcity, rapid population growth and economic development, and overexploitation of water resources [1,2]
To check the reliability of the extended values of air temperature, relative humidity, and canal water temperature obtained from the observations made at AWS-SS using regression Equations (9)–(11), the rate of evaporation from the water flowing through the canal was estimated by the deck surface air layer (DSAL) model using both the observations taken at AWS-Canal and the extended data including the wind speed at 2 m (U2 ) estimated by Equation (8)
The double-deck surface air layer (DSAL) model is an aerodynamic method for estimating the evaporation from a running water surface in irrigation canals
Summary
Many inland river basins in arid and semiarid regions are suffering from the collapse of water resource system and ecology, because of water scarcity, rapid population growth and economic development, and overexploitation of water resources [1,2]. Based on the meteorological measurements made at a lateral canal in the midstream areas of the HRB in 2013, Liu et al [9] have made comparisons between the estimates of canal evaporation by the DSAL model and the heat balance method being used commonly; and they found that there were large differences in daily evaporation between the two approaches, the cumulative evaporation over several days had a difference of about 16%, a value within the range of. The main issues are: (1) To prepare long-term time series of the input data for the DSAL model, including the wind speed, relative humidity, air temperature, and canal water temperature from the meteorological observations made at a nearby automatic weather station by extrapolation and others; (2) to check the reliability of such extended data by comparing the estimates of evaporation rate during the intensive experiment period between the results based on the observations and on the extended data; and (3) to estimate the total evaporation loss from the whole irrigation canal network during the whole irrigation period
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