Simulation model of water temperature variation in dual‐purpose canals considering return flow from upstream paddy fields

Abstract

High ambient air and water temperatures can cause high-temperature damage to ripening rice grains after rice heading and has recently become a major issue of concern. Spill-over irrigation (also referred to as continuous irrigation with running water) is an effective countermeasure that involves simultaneous irrigation and drainage to reduce the ponded water temperature in paddy fields. However, it is necessary to understand the impact of this technique on downstream water temperatures. In this study, the discharge and water temperature variations in a dual-purpose canal (also referred to as irrigationcum-drainage canal) were measured along the main canal of the Tedori-gawa Shichika canal system in Japan. The discharge and water temperature variations in a branch drainage canal were also monitored to analyse the influence of the return flow on the water temperature in the main canal. Based on these observations, a new numerical model was developed to simulate the water temperature variations in the main canal considering meteorological conditions, heat transfer of water in the open canal, and return flow from upstream paddy fields. Finally, the model was applied to examine possible global warming scenarios and discuss the effectiveness of paddy water management in mitigating high-temperature damage in downstream paddy fields. K E Y W O R D S climate change, heat balance, high-temperature damage to rice grains, repeated use of water, spillover irrigation and paddy water management

Statistical evaluation of a long‐memory process using the generalized entropic value‐at‐risk

“…The alluvial fan of the river has an area of 170 km 2 , which is covered by paddy fields. Thus, the hydrology of Tedori River is important for assessing the paddy, surface water, and groundwater environments in the study area (Kimura et al, 2022; Takase & Fujihara, 2019). Studies on the impacts of extensive human intervention to Tedori River have focused on the riparian vegetation and river morphology, and they have shown that dams have modulated the sediment budget and hence the riverbed dynamics (Dang et al, 2014; Nallaperuma & Asaeda, 2020).…”

Non-Destructive Detection Of An Artificial Defect In Concrete With Infrared Thermography And Heat Balance Simulation

“…The sensible heat flux 𝐻𝐻 in the first term on the right side of Equation ( 1) is expressed by Equation (3), , (3) where ca is the specific heat of air (J/kg/K), ρa is the density of air (kg/m 3 ), CHU is the exchange speed of the sensible heat flux (m/s), and Ta is the air temperature (K). CHU depends on the surface characteristics.…”

“…A heat balance means an energy flux balance. This simulation is often used to calculate water [3,4] and ground surface temperatures [5] on a macro scale. This study tries to use this idea for calculating concrete surface temperatures.…”