Evaporation loss and energy balance of agricultural reservoirs covered with counterweighted spheres in arid region

Ke-Wu Han, Ke-Bin Shi and Xin-Jun Yan

Agricultural Water Management, 2020, vol. 238, issue C

Abstract: This study aims at evaluating the impact of counterweighted spheres on evaporation loss in agricultural reservoirs. To this end, water temperatures were measured in two evaporators—one covered with spheres and the other uncovered. Results reveal that during the irrigation period, the average evaporation reduction rate under the coverage of counterweighted spheres equaled 70.6%, average growth rate of the evaporation driving force equaled 19.2%, and average rate of mass-transfer coefficient reduction equaled 75.3%. Between April and August, the observed difference in water-surface temperature between the covered and uncovered groups was significant compared to that during other months. Likewise, for both groups, the water temperature was observed to increase between March and July and reduce between August and October. For the covered group, significant stratification of water temperature was observed between March to July, and the observed difference between the surface temperature (T0w) and that recorded by the lowest sensor (T7w) was the largest (1.9 °C) in July. Between August and October, the said water-temperature stratification was observed to gradually disappear with the difference between T0w and T7w being the smallest (0.2 °C) in October. For the uncovered group, the observed water-temperature stratification was not significant during the entire irrigation period. As observed, 33.6% of the net radiation of the covered group was used for evaporation consumption (latent heat flux), whereas the remaining 66.4% was transmitted to the atmosphere via heat transfer. Findings of this study reveal that sphere coverage serves to reduce evaporation and increase the amount of water required for irrigation. Although economic benefits of this technology were not observed to be significant, the amount of water saved can be used for supplying to irrigated areas. The proposed technology is economically feasible in terms of the net profit from crops produced per m3 of water.

Keywords: Agricultural reservoir; Arid region; Counterweight sphere; Evaporation reduction rate; Microclimate; Energy balance (search for similar items in EconPapers)
Date: 2020
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Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:agiwat:v:238:y:2020:i:c:s0378377419320645

DOI: 10.1016/j.agwat.2020.106227

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