Environmental risk assessment of impacts due to agricultural subsurface drainage practices can benefit from information on drainage system outlet locations along ditches and streams. Unmanned aerial vehicle (UAV) thermal infrared (TIR) surveys may provide a means, through thermal response recognition, to map these subsurface drainage system pipe outlets. Consequently, the objective of this research was to provide a preliminary feasibility assessment on the applicability of UAV TIR imagery for locating these drainage system outlets. Drainage outlet detection with UAV TIR surveys was tested at five sites in Ohio, U.S.A. with a range of waterway sizes from drainage ditch to small and larger streams. There were four key findings from this preliminary study. (1) The UAV TIR surveys detected the ditch/stream water thermal responses associated with drainage system pipe outlets at both a drainage ditch and a small stream. This thermal response is characterized by a ditch/stream water change in apparent radiant temperature (T_rad) from upgradient of the outlet to downgradient of the outlet. (2) As shown by one example in this study, the outlet thermal response in cold winter months, when detectable, is likely the reverse of that obtained during warmer periods of the year. (3) The detected thermal response is rather subtle, exhibiting around a 1 °C ditch/stream water T_rad change from upgradient of the outlet to downgradient of the outlet. (4) The UAV TIR surveys did not detect thermal responses associated with drainage system pipe outlets at three sites with larger sized streams. Since other factors in drainage ditches and streams may produce water T_rad variations that are of the same magnitude of a drainage system pipe outlet thermal response, the use of UAV TIR imagery as a means to map drainage system outlet locations might not be completely practical; however, more investigation is certainly warranted.

对农业地下排水做法造成的影响的环境风险评估可以从排水系统出口沿沟渠和溪流的位置信息中受益。无人驾驶飞行器 (UAV) 热红外 (TIR) 调查可以通过热响应识别提供一种方法来绘制这些地下排水系统管道出口的地图。因此，本研究的目的是对无人机 TIR 图像在定位这些排水系统出口的适用性提供初步可行性评估。在美国俄亥俄州的五个地点使用无人机 TIR 调查对排水口检测进行了测试，水道尺寸范围从排水沟到小型和大型溪流。这项初步研究有四个主要发现。(1) 无人机 TIR 调查在排水沟和小溪流处检测到与排水系统管道出口相关的沟渠/溪流水热响应。这种热响应的特征在于表观辐射温度的沟渠/溪流水变化（T _rad ) 从出口上升到出口下降。(2) 如本研究中的一个例子所示，寒冷冬季月份的出口热响应在可检测到的情况下，可能与一年中较温暖时期的出口热响应相反。(3) 检测到的热响应相当微妙，从出口上升到出口下降的沟渠/溪流水T _{rad变化约为 1°C。}(4) UAV TIR 调查未检测到与排水系统管道出口相关的三个具有较大河流的地点的热响应。由于排水沟渠和溪流中的其他因素可能会产生水T _rad与排水系统管道出口热响应具有相同幅度的变化，使用无人机 TIR 图像作为绘制排水系统出口位置的一种手段可能并不完全实用；但是，肯定需要进行更多调查。