On the attribution of the changing hydrological cycle in Poyang Lake Basin, China

Hydrol. Earth Syst. Sci.

McNulty

et al. 2017

Abstract. The evapotranspiration / potential evapotranspiration (AET / PET) ratio is traditionally termed as the crop coefficient (K c ) and has been generally used as ecosystem evaporative stress index. In the current hydrology literature, K c has been widely used as a parameter to estimate crop water demand by water managers but has not been well examined for other types of ecosystems such as forests and other perennial vegetation. Understanding the seasonal dynamics of this variable for all ecosystems is important for projecting the ecohydrological responses to climate change and accurately quantifying water use at watershed to global scales. This study aimed at deriving monthly K c for multiple vegetation cover types and understanding its environmental controls by analyzing the accumulated global eddy flux (FLUXNET) data. We examined monthly K c data for seven vegetation covers, including open shrubland (OS), cropland (CRO), grassland (GRA), deciduous broad leaf forest (DBF), evergreen needle leaf forest (ENF), evergreen broad leaf forest (EBF), and mixed forest (MF), across 81 sites. We found that, except for evergreen forests (EBF and ENF), K c values had large seasonal variation across all land covers. The spatial variability of K c was well explained by latitude, suggesting site factors are a major control on K c . Seasonally, K c increased significantly with precipitation in the summer months, except in EBF. Moreover, leaf area index (LAI) significantly influenced monthly K c in all land covers, except in EBF. During the peak growing season, forests had the highest K c values, while croplands (CRO) had the lowest. We developed a series of multivariate linear monthly regression models for K c by land cover type and season using LAI, site latitude, and monthly precipitation as independent variables. The K c models are useful for understanding water stress in different ecosystems under climate change and variability as well as for estimating seasonal ET for large areas with mixed land covers.

mentioning

confidence: 99%

Environmental controls on seasonal ecosystem evapotranspiration/potential evapotranspiration ratio as determined by the global eddy flux measurements

Liu

Hydrol. Earth Syst. Sci.

McNulty

et al. 2017

“…However, the ability to predict the impacts of extreme events presents considerable challenges to existing models [45]. Performance of watershed-scale models, lumped models in particular, is often evaluated on data that have been averaged in space and time [41] and this precludes evaluation of performance of extreme events [46][47][48] such as drought and flooding events. Where finer resolution evaluations have been conducted, model performance of most hydrologic models is often poor, especially for drought conditions.…”

Section: Extreme Events Challenge Existing Modeling Toolsmentioning

confidence: 99%

Forest Management Challenges for Sustaining Water Resources in the Anthropocene

Vose

2016

Forests

Abstract:The Earth has entered the Anthropocene epoch that is dominated by humans who demand unprecedented quantities of goods and services from forests. The science of forest hydrology and watershed management generated during the past century provides a basic understanding of relationships among forests and water and offers management principles that maximize the benefits of forests for people while sustaining watershed ecosystems. However, the rapid pace of changes in climate, disturbance regimes, invasive species, human population growth, and land use expected in the 21st century is likely to create substantial challenges for watershed management that may require new approaches, models, and best management practices. These challenges are likely to be complex and large scale, involving a combination of direct and indirect biophysical watershed responses, as well as socioeconomic impacts and feedbacks. We discuss the complex relationships between forests and water in a rapidly changing environment, examine the trade-offs and conflicts between water and other resources, and propose new management approaches for sustaining water resources in the Anthropocene.

“…Additionally, elevated CO 2 and climate change can also execrate impacts on hydrological and ecosystem productivity through changing water use efficiency (Miller-Rushing et al, 2009;de Kauwe et al, 2013;Zhang, F. et al, 2014;Liu et al, 2015) and vegetation processes (e.g., stomatal conductance and LAI; Sun et al, 2014). However, the WaSSI model did not consider these effects, potentially resulting in errors in estimating ET, GPP, or water yield (Cox et al, 2000;Gedney et al, 2006;Oki and Kanae, 2006;Betts et al, 2007;Piao et al, 2007).…”

Section: Uncertaintiesmentioning

confidence: 99%

“…Mounting evidence has suggested that climate and its change has played an important role in controlling the water cycle by changes in evaporation, transpiration, and runoff (McCabe, 2002;Hamlet et al, 2007;Syed et al, 2010;Wang and Hejazi, 2011;Chien et al, 2013;Hegerl et al, 2014;Huntington and Billmire, 2014;McCabe and Wolock, 2014;Sun et al, 2014). Also, climate can exert a dominant control on vegetation structural and phenological characteristics through variations in air temperature, precipitation, solar radiation, wind, and CO 2 concentration (Nemani et al, 2003;Harding et al, 2011;Wang et al, 2014;Zhang, F. et al, 2014;.…”

Section: Introductionmentioning

confidence: 99%

Projecting water yield and ecosystem productivity across the United States by linking an ecohydrological model to WRF dynamically downscaled climate data

Hydrol. Earth Syst. Sci.

Cohen

et al. 2016

Self Cite

Abstract. Quantifying the potential impacts of climate change on water yield and ecosystem productivity is essential to developing sound watershed restoration plans, and ecosystem adaptation and mitigation strategies. This study links an ecohydrological model (Water Supply and Stress Index, WaSSI) with WRF (Weather Research and Forecasting Model) using dynamically downscaled climate data of the HadCM3 model under the IPCC SRES A2 emission scenario. We evaluated the future (2031-2060) changes in evapotranspiration (ET), water yield (Q) and gross primary productivity (GPP) from the baseline period of 1979-2007 across the 82 773 watersheds (12-digit Hydrologic Unit Code level) in the coterminous US (CONUS). Across the CONUS, the future multi-year means show increases in annual precipitation (P ) of 45 mm yr −1 (6 %), 1.8 • C increase in temperature (T ), 37 mm yr −1 (7 %) increase in ET, 9 mm yr −1 (3 %) increase in Q, and 106 gC m −2 yr −1 (9 %) increase in GPP. We found a large spatial variability in response to climate change across the CONUS 12-digit HUC watersheds, but in general, the majority would see consistent increases all variables evaluated. Over half of the watersheds, mostly found in the northeast and the southern part of the southwest, would see an increase in annual Q (> 100 mm yr −1 or 20 %). In addition, we also evaluated the future annual and monthly changes of hydrology and ecosystem productivity for the 18 Water Resource Regions (WRRs) or two-digit HUCs. The study provides an integrated method and example for comprehensive assessment of the potential impacts of climate change on watershed water balances and ecosystem productivity at high spatial and temporal resolutions. Results may be useful for policy-makers and land managers to formulate appropriate watershed-specific strategies for sustaining water and carbon sources in the face of climate change.