Assessment of Spatiotemporal Variability of Evapotranspiration and Its Governing Factors in a Mountainous Watershed

Abstract

Evapotranspiration (ET) is a key component of the water balance, which influences hydrometeorology, water resources, carbon and other biogeochemical cycles, and ecosystem diversity. This study aims to investigate the spatio-temporal variations of ET at the East River watershed in Colorado and analyze the factors that control these variations. ET was acquired using the community land model (CLM) simulations and was compared with the values estimated using Fu’s equation and a watershed-scale water balance equation. The simulation results showed that 55% of annual precipitation in the East River is lost to ET, in which 75% of the ET comes from the summer months (May to September). We also found that the contribution of transpiration to the total ET was ~50%, which is much larger than that of soil evaporation (32%) and canopy evaporation (18%). Spatial analysis indicated that the ET is greater at elevations of 2950–3200 m and lower along the river valley (<2750 m) and at the high elevations (>3900 m). A correlation analysis of factors affecting ET showed that the land elevation, air temperature, and vegetation are closely correlated and together they govern the ET spatial variability. The results also suggested that ET in areas with more finely textured soil is slightly larger than regions with coarse-texture soil. This study presents a promising approach to the assessment of ET with a high spatiotemporal resolution over watershed scales and investigates factors controlling ET spatiotemporal variations.

The Importance of Interflow to Groundwater Recharge in a Snowmelt‐Dominated Headwater Basin

“…This is higher than basin‐wide ER estimates by Tran et al () at 550 mm/year for elevations 2,950 to 3,200 m and 300 mm/year at higher elevations. However, our inclusion of snow redistribution as well as lateral flow and groundwater to subsidize ET is not accounted for by Tran et al () and may explain differences in results. With reasonable water budget components, we can move toward answering questions pertaining to groundwater.…”

“…We estimate total average annual ET losses in CC at 623±50 mm/year. This is higher than basin-wide ER estimates by Tran et al (2019) at 550 mm/year for elevations 2,950 to 3,200 m and 300 mm/year at higher elevations. However, our inclusion of snow redistribution as well as lateral flow and groundwater to subsidize ET is not accounted for by Tran et al (2019) and may explain differences in results.…”

Depth‐ and Time‐Resolved Distributions of Snowmelt‐Driven Hillslope Subsurface Flow and Transport and Their Contributions to Surface Waters

“…The underlying soil along the hillslope was relatively drier, reflecting efficient evapotranspiration and lack of deep infiltration during summer. As noted earlier, the CLM-based calculations (Tran et al, 2019) for the summer months (WY2016, 2017, 2018) predicted that ET was large enough to prevent net infiltration of monsoon precipitation at this site. Although not part of the hillslope, the floodplain station PLM4 is included for contrast, with its higher water contents and potentials resulting from a shallow depth to the water table (0.76 m bgs during sampling) and higher clay content.…”

“…(b) Monthly water content of snow and monsoon rainfall (CREST4). (c) Daily and cumulative ET calculated with the CML (Tran et al, 2019).…”

Spatiotemporal Variation of Drought and Associated Multi-Scale Response to Climate Change over the Yarlung Zangbo River Basin of Qinghai–Tibet Plateau, China

“…Long-term scPDSI anomaly variation in the YZR basin was strong negatively correlated with DTR, by a correlation coefficient of −0.70 in the original time series (Figure 9a). Some studies concluded that changes of PET were dominated by temperature variables [104][105][106]. Although DTR is an important indicator of temperature, it showed a non-significantly correlation with changes of PET in the YZR basin as their correlation coefficient was only 0.36.…”