The low-temperature outflow from large hydropower projects can have adverse effects on downstream ecosystems and on crops requiring irrigation. This study, which integrates prototype observations with numerical models, examined the influence of different water withdrawal schemes on the thermal structure of reservoir water and proposed measures to mitigate the impact of low-temperature outflows. The results indicate that from May to October, the thermocline under the single-level withdrawal scheme (S1) descended by an average of 11.7 m more than that under the stratified withdrawal scheme (S2). Moreover, from May to August, the outflow temperature under S2 was consistently higher than under S1, by an average of about 3.5 ℃. Specifically, during the irrigation period, the average water temperatures for S1 and S2 were 15.6 ℃ and 18.5 ℃, respectively, resulting in a difference of 2.9 ℃. Consequently, during the irrigation season, the irrigation water temperature under the S1 scheme failed to meet the minimum temperature requirements for 35.4% of the total irrigation days, whereas the S2 scheme consistently met these requirements. For the S1 scheme, measures involving the substitution of low-temperature outflow with warm water from natural rivers were proposed, with an extraction flow rate ranging from 0.005 to 0.185 m3/s. This research provides technical support and guidance for management authorities to mitigate the impact of releasing cold water.