Effects of irrigation on the water and energy balances of the Colorado and Mekong river basins

Abstract

An irrigation scheme, based on simulated soil moisture deficit, has been included in the variable infiltration capacity macroscale hydrologic model. Water withdrawals are taken from the nearest river, or, in periods of water scarcity, from reservoirs. Alternatively, water can be assumed freely available. The irrigation scheme successfully simulates crop consumptive water use in large river basins. In general, irrigation leads to decreased streamflow and increased evapotranspiration. The locally significant increases in evapotranspiration (or latent heat) results in lower surface temperatures, and hence decreased sensible heat flux. Simulations performed for a 20-year period for the Colorado and Mekong river basins indicate irrigation water requirements of 10 and 13.4 km 3 year K1 , respectively, corresponding to streamflow decreases of 37 and 2.3%. The increase in latent heat flux is accompanied by a decrease in annual averaged surface temperatures of 0.04 8C for both river basins. The maximum simulated increase in latent heat flux averaged over the three peak irrigation months for one grid cell is 63 W m K2 , where surface temperature decreases 2.1 8C. Simulated actual water use is somewhat less than simulated irrigation water requirements; 8.3 and 12.4 km 3 year K1 for the Colorado and Mekong river basin, respectively. q

Improving the representation of hydrologic processes in Earth System Models

“…CLM has been developed to represent maize, soybean, and spring wheat including management practices such as fertilizer application, residue management, and harvest [Drewniak et al, 2013]; irrigation from surface water [Sacks et al, 2009;Leng et al, 2013] and from groundwater [Leng et al, 2014]. VIC [Liang et al, 1994] has been fully coupled to a cropping system model (CropSyst), allowing for simulation of the interactions between large-scale hydrologic processes and crop growth, phenology, and management (including irrigation technology and management) ; and it has been adapted to simulate reservoir operations [Haddeland et al, 2006]. Other modeling frameworks that allow for representation of water management include WaterGap [Alcamo et al, 2003] the Model for Scale Adaptive River Transport (MOSART), which is a streamflow routing model that has been incorporated into an ESM framework [Li et al, 2015] and coupled with a water management model [Voisin et al, 2013a] and an integrated assessment model [Voisin et al, 2013b] to simulate water demand consistent with the socioeconomic scenarios.…”

Detecting the long-term impacts from climate variability and increasing water consumption on runoff in the Krishna river basin (India)

“…In particular developments in water storage in reservoirs and consumption for irrigation and industry cause increased evaporation and substantial effects on river runoff (e.g. Döll and Siebert, 2002;De Rosnay et al, 2003;Haddeland et al, 2006). Water consumption may affect the annual water budget, while the structures that capture water such as dams and reservoirs may change the patterns of the annual hydrological cycle.…”

Seasonal effects of irrigation on land–atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin

“…Zeng et al: Seasonal effects of irrigation on land-atmosphere latent heat be returned to the atmosphere (Kendig et al, 2000;. This results in a direct augmentation of the latent heat flux (LH) from land to atmosphere (Haddeland et al, 2006). In addition, the irrigation changes the partitioning of net radiation available at the surface into LH and sensible heat (SH) (Bowen ratio) (Meijninger and De Bruin, 2000).…”