Dong Zhaokai, Bain Daniel J, Paudel Shishir, Buck John K, Ng Carla
Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Sci Total Environ. 2024 Nov 20;952:175747. doi: 10.1016/j.scitotenv.2024.175747. Epub 2024 Aug 26.
Evapotranspiration (ET) is an important water budget term for understanding the recovery of stormwater retention in green roof systems (GRs). However, ET evaluations, particularly in full-scale GRs, remain challenging. This study investigated ET dynamics within a GR in the City of Pittsburgh, USA, using a water balance based on continuously monitored soil moisture from moisture sensors over 15 months. Results suggest under well-watered soil conditions, daily moisture loss correlated with solar radiation, temperature, and humidity, in decreasing order of correlation strength, while wind speed had limited effects. Compared to sensor-informed moisture loss (using moisture-based water balance), the Hargreaves and FAO-56 Penman-Monteith equations predicted cumulative ET that was 1.8 and 2.1 times higher, respectively. When soil moisture declined and approached the temporary wilting points, a noticeable reduction in daily moisture loss was observed. This suggests the necessity of using a water stress coefficient alongside a crop coefficient to represent actual ET based on FAO-56 Penman-Monteith estimates. Seasonal crop coefficients from dominant native plant species present at our monitored location, eastern bluestar (Amsonia tabernaemontana) and creeping woodsorrel (Oxalis corniculata), had mean values of 0.48, 0.62, and 0.65 for fall, spring, and summer, respectively. The impact of water stress on ET could be characterized by a linear relationship with moisture content. Our results highlight the importance of soil moisture in regulating ET processes and demonstrate the utility of soil moisture data for evaluating ET in GRs and informing irrigation practices.
蒸发散（ET）是理解绿色屋顶系统（GRs）中雨水滞留恢复情况的一个重要水分收支术语。然而，蒸发散评估，尤其是在全尺寸绿色屋顶系统中，仍然具有挑战性。本研究利用基于湿度传感器连续监测土壤湿度的水平衡，对美国匹兹堡市一个绿色屋顶系统内的蒸发散动态进行了调查，为期15个月。结果表明，在土壤水分充足的条件下，每日水分损失与太阳辐射、温度和湿度相关，相关强度依次递减，而风速的影响有限。与基于传感器的水分损失（使用基于水分的水平衡）相比，哈格里夫斯方程和粮农组织-56彭曼-蒙特斯方程预测的累积蒸发散分别高出1.8倍和2.1倍。当土壤水分下降并接近暂时萎蔫点时，每日水分损失明显减少。这表明有必要根据粮农组织-56彭曼-蒙特斯估计值，使用水分胁迫系数和作物系数来表示实际蒸发散。在我们监测地点存在的优势本土植物物种，即东部蓝星（Amsonia tabernaemontana）和酢浆草（Oxalis corniculata）的季节性作物系数，秋季、春季和夏季的平均值分别为0.48、0.62和0.65。水分胁迫对蒸发散的影响可以用与土壤水分含量的线性关系来表征。我们的结果突出了土壤水分在调节蒸发散过程中的重要性，并证明了土壤水分数据在评估绿色屋顶系统蒸发散和指导灌溉实践方面的实用性。
