scholarly journals Trends in evapotranspiration and its drivers in Great Britain: 1961 to 2015

2018 ◽  
Author(s):  
Eleanor M. Blyth ◽  
Alberto Martinez-de la Torre ◽  
Emma L. Robinson
Keyword(s):  
Soil Moisture ◽  
Great Britain ◽  
Water Budget ◽  
River Flow ◽  
Potential Evapotranspiration ◽  
Evaporative Demand ◽  
East Anglia ◽  
Meteorological Forcing ◽  
Physically Based Model ◽  
Physically Based

Abstract. In a warming climate, the water budget of the land is subject to varying forces such as increasing evaporative demand, mainly through the increased temperature, and changes to the precipitation, which might go up or down. Using a verified, physically based model with 55 years of observation-based meteorological forcing, an analysis of the water budget demonstrates that Great Britain is getting warmer and wetter. Increases in precipitation (3.0 ± 2.0 mm yr−1 yr−1) and air temperature (0.20 ± 0.13 K decade−1) are driving increases in river flow (2.16 mm yr−1 yr−1) and evapotranspiration (0.87 mm yr−1 yr−1), with no significant trend in the soil moisture. The change in evapotranspiration is roughly constant across the regions whereas runoff varies greatly between regions: the biggest change is seen in Scotland (4.56 mm yr−1 yr−1), where precipitation increases were also the greatest (5.4 ± 3.0 mm yr−1 yr−1) and smallest trend (0.29 mm yr−1 yr−1) is seen in the English Lowlands (East Anglia and Midlands), where the increase in rainfall is not statistically significant (1.1 ± 0.7 mm yr−1 yr−1). Relative to their contribution to the evapotranspiration budget, the increase in interception is higher than the other components. This is due to the fact that it correlates strongly with precipitation which is seeing a greater increase than the potential evapotranspiration. This leads to a higher increase in actual evapotranspiration that the potential evapotranspiration, and a negligible increase in soil moisture or groundwater store.

scholarly journals Trends in evapotranspiration and its drivers in Great Britain: 1961 to 2015

2019 ◽  
Vol 43 (5) ◽  
pp. 666-693 ◽  
Author(s):  
Eleanor M Blyth ◽  
Alberto Martínez-de la Torre ◽  
Emma L Robinson
Keyword(s):  
Soil Moisture ◽  
Great Britain ◽  
Water Budget ◽  
Potential Evapotranspiration ◽  
Evaporative Demand ◽  
East Anglia ◽  
Meteorological Forcing ◽  
Physically Based Model ◽  
Warming Climate ◽  
Physically Based

In a warming climate, the water budget of the land is subject to varying forces such as increasing evaporative demand, mainly through the increased temperature, and changes to the precipitation, which might go up or down. Using a verified, physically based model with 55 years of observation-based meteorological forcing, an analysis of the water budget demonstrates that Great Britain is getting warmer and wetter. Increases in precipitation (2.96.0 ± 2.03 mm yr–1 yr–1) and air temperature (0.20 ± 0.13 K decade–1) are driving increases in runoff (2.18 ± 1.84 mm yr–1 yr–1) and evapotranspiration (0.87 ± 0.55 mm yr–1 yr–1), with no significant trend in the soil moisture. The change in evapotranspiration is roughly constant across the regions, whereas runoff varies greatly between regions: the biggest change is seen in Scotland (4.56 ± 2.82 mm yr–1 yr–1), where precipitation increases were also the greatest (5.4 ± 3.0 mm yr–1 yr–1), and the smallest trend (0.33 ± 1.50 mm yr–1 yr–1, not statistically significant) is seen in the English Lowlands (East Anglia and Midlands), where the increase in rainfall is not statistically significant (1.07 ± 1.76 mm yr–1 yr–1). Relative to its contribution to the evapotranspiration budget, the increase in interception is higher than the other components. This is due to the fact that it correlates strongly with precipitation, which is seeing a greater increase than the potential evapotranspiration. This leads to a higher increase in actual evapotranspiration than the potential evapotranspiration, and a negligible increase in soil moisture or groundwater store.

scholarly journals Impact of precipitation and increasing temperatures on drought in eastern Africa

2019 ◽  
Author(s):  
Sarah F. Kew ◽  
Sjoukje Y. Philip ◽  
Mathias Hauser ◽  
Mike Hobbins ◽  
Niko Wanders ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Potential Evapotranspiration ◽  
A Priori ◽  
Agricultural Drought ◽  
Eastern Africa ◽  
Precipitation Trend ◽  
Crop Failure ◽  
Evaporative Demand ◽  
Clear Trend ◽  
The Impact

Abstract. In eastern Africa droughts can cause crop failure and lead to food insecurity. With increasing temperatures, there is an a priori assumption that droughts are becoming more severe, however, the link between droughts and climate change is not sufficiently understood. In the current study we focus on agricultural drought and the influence of high temperatures and precipitation deficits on this. Using a combination of models and observational datasets, we studied trends in six regions in eastern Africa in four drought-related annually averaged variables – soil moisture, precipitation, temperature and, as a measure of evaporative demand, potential evapotranspiration (PET). In standardized soil moisture data, we find no discernible trends. Precipitation was found to have a stronger influence on soil moisture variability than temperature or PET, especially in the drier, or water-limited, study regions. The error margins on precipitation-trend estimates are however large and no clear trend is evident. We find significant positive trends in local temperatures. However, the influence of these on soil moisture annual trends appears limited as evaporation is water limited. The trends in PET are predominantly positive, but we do not find strong relations between PET and soil moisture trends. Nevertheless, the PET-trend results can still be of interest for irrigation purposes as it is PET that determines the maximum evaporation rate. We conclude that, until now, the impact of increasing local temperatures on agricultural drought in eastern Africa is limited and recommend that any soil moisture analysis be supplemented by analysis of precipitation deficit.

EVAPOTRANSPIRATION AND LEAF WATER STATUS OF ALFALFA GROWING UNDER ADVECTIVE CONDITIONS

1981 ◽  
Vol 61 (3) ◽  
pp. 601-607 ◽  
Author(s):  
R. J. WILLIAMS ◽  
DARRYL G. STOUT
Keyword(s):  
Soil Moisture ◽  
Potential Evapotranspiration ◽  
Water Status ◽  
Bowen Ratio ◽  
High Rate ◽  
Leaf Water Status ◽  
Leaf Osmotic Potential ◽  
Physically Based ◽  
Environmental Demand ◽  
Moisture Conditions

Actual evapotranspiration (LE) and leaf osmotic potential (ψs) were measured on a Medicago sativa L. (alfalfa, cv. Thor) field in interior British Columbia that is subject to advection. During periods of advection, LE, measured by the Bowen ratio energy balance method, exceeded both the net radiation (Q*) and the potential evapotranspiration (PE) calculated by the physically based formula of Priestley and Taylor (1972). During advection, Q* was a better approximation of LE than was PE. During nonadvection periods, LE was approximately equal to PE. It was found that the Jury and Tanner (1975) modification of PE for advective conditions gave favorable results during periods immediately following irrigation. Diurnal measurements revealed that leaf ψs reached a minimum by about 1200 h and then remained constant even though LE continued at a high rate. Leaf ψs measured at 0800 h reflected soil moisture conditions, and leaf ψs measured at 1400 h reflected both soil moisture conditions and environmental demand.

Study of the water budget of streets: experimentation and modelling

2006 ◽  
Vol 54 (6-7) ◽  
pp. 41-48 ◽  
Author(s):  
D. Ramier ◽  
E. Berthier ◽  
P. Dangla ◽  
H. Andrieu
Keyword(s):  
Water Budget ◽  
Storage Capacity ◽  
Sensitivity Study ◽  
Porous Media Flow ◽  
Time Step ◽  
Physically Based Model ◽  
Time Period ◽  
Physically Based ◽  
Runoff Losses ◽  
Rain Events

The study of two stretches of street during 38 months has been performed to analyze the hydrological behavior of streets during rain events. The results show that runoff coefficients are very variable and runoff losses may be important. In order to better understand this behavior, a physically based model has been used. This model, BiL, combines a porous media flow module with a surface runoff module. The lateral runoff transfer in the lateral gutter is approximated by the Muskingum model. Evaporation is simulated by an adaptation of the Penman method. A sensitivity study shows that the model is mainly sensitive to saturated hydraulic conductivity of the asphalt pavement and to the storage capacity. The comparison of simulated and observed data gives good results for the runoff outflow at a 3 minutes time step. Nevertheless, the simulation results are less encouraging for the runoff coefficient. This study of the water budget of two street stretches during a time period of 38 months indicates that the infiltration and evaporation represent between 20 and 30% of rain.

Rainfall-Runoff Simulation and Interpretation in Great Britain using LSTMs

2021 ◽  
Author(s):  
Thomas Lees ◽  
Marcus Buechel ◽  
Bailey Anderson ◽  
Louise Slater ◽  
Steven Reece ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Great Britain ◽  
Concept Formation ◽  
Conceptual Models ◽  
River Flow ◽  
Short Term Memory ◽  
Data Driven ◽  
Hydrological Processes ◽  
Rainfall Runoff ◽  
Runoff Simulation

<p>Techniques from the field of machine learning have shown considerable promise in rainfall-runoff modelling. This research offers three novel contributions to the advancement of this field: a study of the performance of LSTM based models in a GB hydrological context; a diagnosis of hydrological processes that data-driven models simulate well but conceptual models struggle with; and finally an exploration of methods for interpreting the internal cell states of the LSTMs. </p><p>In this study we train two deep learning models, a Long Short Term Memory (LSTM) Network and an Entity Aware LSTM (EALSTM), to simulate discharge for 518 catchments across Great Britain using a newly published dataset, CAMELS-GB. We demonstrate that the LSTM models are capable of simulating discharge for a large sample of catchments across Great Britain, achieving a mean catchment Nash-Sutcliffe Efficiency (NSE) of 0.88 for the LSTM and 0.86 for the EALSTM, where no stations have an NSE < 0. We compare these models against a series of conceptual models which have been externally calibrated and used as a benchmark (Lane et al., 2019). </p><p>Alongside robust performance for simulating discharge, we note the potential for data-driven methods to identify hydrological processes that are present in the underlying data, but the FUSE conceptual models are unable to capture. Therefore, we calculate the relative improvement of the LSTMs compared to the conceptual models, ∆NSE. We find that the largest improvement of the LSTM models compared to our benchmark is in the summer months and in the South East of Great Britain. </p><p>We also demonstrate that the internal “memory” of the LSTM correlates with soil moisture, despite the LSTM not receiving soil moisture as an input. This process of “concept-formation” offers three interesting findings. It provides a novel method for deriving soil moisture estimates. It suggests the LSTM is learning physically realistic representations of hydrological processes. Finally, this process of concept formation offers the potential to explore how the LSTM is able to produce accurate simulations of discharge, and the transformations that are learned from inputs (temperature, precipitation) to outputs (discharge).</p><p>References:<br>Lane, R. A., Coxon, G., Freer, J. E., Wagener, T., Johnes, P. J., Bloomfield, J. P., Greene, S., Macleod, C. J., and Reaney, S. M.: Benchmarking the predictive capability of hydrological models for river flow and flood peak predictions across over 1000 catchments in Great Britain, Hydrology and Earth System Sciences, 23, 4011–4032, 2019.</p>

scholarly journals Derivation of RCM-driven potential evapotranspiration for hydrological climate change impact analysis in Great Britain: a comparison of methods and associated uncertainty in future projections

2013 ◽  
Vol 10 (1) ◽  
pp. 597-624 ◽  
Author(s):  
C. Prudhomme ◽  
J. Williamson
Keyword(s):  
Climate Change ◽  
Great Britain ◽  
Climate Change Impact ◽  
Impact Analysis ◽  
Climate Models ◽  
River Flow ◽  
Potential Evapotranspiration ◽  
Climate Data ◽  
Change Impact ◽  
The Impact

Abstract. Potential evapotranspiration PET is the water that would be lost by plants through evaporation and transpiration if water was not limited in the soil, and it is commonly used in conceptual hydrological modelling in the calculation of runoff production and hence river discharge. Future changes of PET are likely to be as important as changes in precipitation patterns in determining changes in river flows. However PET is not calculated routinely by climate models so it must be derived independently when the impact of climate change on river flow is to be assessed. This paper compares PET estimates from twelve equations of different complexity, driven by the Hadley Centre's HadRM3-Q0 model outputs representative of 1961–1990, with MORECS PET, a product used as reference PET in Great Britain. The results show that the FAO56 version of the Penman-Monteith equations reproduce best the spatial and seasonal variability of MORECS PET across GB when driven by HadRM3-Q0 estimates of relative humidity, total cloud, wind speed and linearly bias-corrected mean surface temperature. This suggests that potential biases in HadRM3-Q0 climate do not result in significant biases when the physically-based FAO56 equations are used. Percentage changes in PET between the 1961–1990 and 2041–2070 time slices were also calculated for each of the twelve PET equations. Results show a large variation in the magnitude (and sometimes direction) of changes estimated from different PET equations, with Turc, Jensen-Hense and calibrated Blaney-Criddle methods systematically projecting the largest increases across GB for all months and Priestley-Taylor, Makkink and Thornthwaite showing the smallest changes. We recommend the use of the FAO56 equation as when driven by HadRM3-Q0 climate data this best reproduces the reference MORECS PET across Great Britain for the reference period of 1961–1990. Further, the future changes of PET estimated by FAO56 are within the range of uncertainty defined by the ensemble of twelve PET equations. The changes show a clear northwest-southeast gradient of PET increase with largest (smallest) changes in the northwest in January (July and October) respectively. However, the range in magnitude of PET changes due to the choice of PET method shown in this study for Great Britain suggests that PET uncetainty is perhaps one of the greatest challenges facing the assessment of climate change impact on hydrology.

scholarly journals Future Flows Climate: an ensemble of 1-km climate change projections for hydrological application in Great Britain

2012 ◽  
Vol 4 (1) ◽  
pp. 143-148 ◽  
Author(s):  
C. Prudhomme ◽  
S. Dadson ◽  
D. Morris ◽  
J. Williamson ◽  
G. Goodsell ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Great Britain ◽  
River Flow ◽  
Potential Evapotranspiration ◽  
Time Step ◽  
Climate Change Projections ◽  
Groundwater Levels ◽  
Temperature And Precipitation ◽  
Climate Change Uncertainty

Abstract. The dataset Future Flows Climate was developed as part of the project ''Future Flows and Groundwater Levels'' to provide a consistent set of climate change projections for the whole of Great Britain at both space and time resolutions appropriate for hydrological applications, and to enable climate change uncertainty and climate variability to be accounted for in the assessment of their possible impacts on the environment. Future Flows Climate is derived from the Hadley Centre's ensemble projection HadRM3-PPE that is part of the basis of UKCP09 and includes projections in available precipitation (water available to hydrological processes after snow and ice storages have been accounted for) and potential evapotranspiration. It corresponds to an 11-member ensemble of transient projections from January 1950 to December 2098, each a single realisation from a different variant of HadRM3. Data are provided on a 1-km grid over the HadRM3 land areas at a daily (available precipitation) and monthly (PE) time step as netCDF files. Because systematic biases in temperature and precipitation were found between HadRM3-PPE and gridded temperature and precipitation observations for the 1962–1991 period, a monthly bias correction procedure was undertaken, based on a linear correction for temperature and a quantile-mapping correction (using the gamma distribution) for precipitation followed by a spatial downscaling. Available precipitation was derived from the bias-corrected precipitation and temperature time series using a simple elevation-dependant snow-melt model. Potential evapotranspiration time series were calculated for each month using the FAO-56 Penman-Monteith equations and bias-corrected temperature, cloud cover, relative humidity and wind speed from HadRM3-PPE along with latitude of the grid and the day of the year. Future Flows Climate is freely available for non-commercial use under certain licensing conditions. It is the dataset used to generate Future Flows Hydrology, an ensemble of transient projections of daily river flow and monthly groundwater time series for representative river basins and boreholes in Great Britain. doi:10.5285/bad1514f-119e-44a4-8e1e-442735bb9797.

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