Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change

Understanding the trends of reference evapotranspiration (ETo) and its influential meteorological variables due to climate change is required for studying the hydrological cycle, vegetation restoration, and regional agricultural production. Although several studies have evaluated these trends, they suffer from a number of drawbacks: (1) they used data series of less than 50 years; (2) they evaluated the individual impact of a few climatic variables on ETo, and thus could not represent the interactive effects of all forces driving trends of ETo; (3) they mostly studied trends of ETo and meteorological variables in similar climate regions; (4) they often did not eliminate the impact of serial correlations on the trends of ETo and meteorological variables; and finally (5) they did not study the extremum values of meteorological variables and ETo. This study overcame the abovementioned shortcomings by (1) analyzing the 50-year (1961–2010) annual trends of ETo and 12 meteorological variables from 18 study sites in contrasting climate types in Iran, (2) removing the effect of serial correlations on the trends analysis via the trend-free pre-whitening approach, (3) determining the most important meteorological variables that control the variations of ETo, and (4) evaluating the coincidence of annual extremum values of meteorological variables and ETo. The results showed that ETo and several meteorological variables (namely wind speed, vapor pressure deficit, cloudy days, minimum relative humidity, and mean, maximum and minimum air temperature) had significant trends at the confidence level of 95% in more than 50% of the study sites. These significant trends were indicative of climate change in many regions of Iran. It was also found that the wind speed (WS) had the most significant influence on the trend of ETo in most of the study sites, especially in the years with extremum values of ETo. In 83.3% of the study sites (i.e., all arid, Mediterranean and humid regions and 66.7% of semiarid regions), both ETo and WS reached their extremum values in the same year. The significant changes in ETo due to WS and other meteorological variables have made it necessary to optimize cropping patterns in Iran.

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Assessment of the impact of climate change on the freshwater availability of Kaduna River basin, Nigeria

Journal of Water and Land Development ◽

10.2478/jwld-2018-0047 ◽

2018 ◽

Vol 38 (1) ◽

pp. 105-114 ◽

Cited By ~ 2

Author(s):

Gloria C. Okafor ◽

Kingsley N. Ogbu

Keyword(s):

Climate Change ◽

River Basin ◽

Water Availability ◽

Hydrological Cycle ◽

Temporal Trends ◽

Kendall Test ◽

Well Being ◽

Trend Test ◽

Climate Indices ◽

The Impact

AbstractChanges in runoff trends have caused severe water shortages and ecological problems in agriculture and human well-being in Nigeria. Understanding the long-term (inter-annual to decadal) variations of water availability in river basins is paramount for water resources management and climate change adaptation. Climate change in Northern Nigeria could lead to change of the hydrological cycle and water availability. Moreover, the linkage between climatic changes and streamflow fluctuations is poorly documented in this area. Therefore, this study examined temporal trends in rainfall, temperature and runoff records of Kaduna River basin. Using appropriate statistical tools and participatory survey, trends in streamflow and their linkages with the climate indices were explored to determine their amplifying impacts on water availability and impacts on livelihoods downstream the basin. Analysis indicate variable rainfall trend with significant wet and dry periods. Unlike rainfall, temperature showed annual and seasonal scale statistically increasing trend. Runoff exhibit increasing tendency but only statistically significant on annual scale as investigated with Mann–Kendall trend test. Sen’s estimator values stood in agreement with Mann–Kendall test for all variables. Kendall tau and partial correlation results revealed the influence of climatic variables on runoff. Based on the survey, some of the hydrological implications and current water stress conditions of these fluctuations for the downstream inhabitants were itemized. With increasing risk of climate change and demand for water, we therefore recommend developing adaptive measures in seasonal regime of water availability and future work on modelling of the diverse hydrological characteristics of the entire basin.

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Vulnerability of coastal areas to increased aquifer saturation due to climate change

10.5194/egusphere-egu21-14870 ◽

2021 ◽

Author(s):

Alexandre Gauvain ◽

Ronan Abhervé ◽

Jean-Raynald de Dreuzy ◽

Luc Aquilina ◽

Frédéric Gresselin

Keyword(s):

Climate Change ◽

Sea Level ◽

Large Scale ◽

Regional Scale ◽

Drainage System ◽

Hydrological Regime ◽

Coastal Areas ◽

Western Coast ◽

Study Sites ◽

The Impact

Like in other relatively flat coastal areas, flooding by aquifer overflow is a recurring problem on the western coast of Normandy (France). Threats are expected to be enhanced by the rise of the sea level and to have critical consequences on the future development and management of the territory. The delineation of the increased saturation areas is a required step to assess the impact of climate change locally. Preliminary models showed that vulnerability does not result only from the sea side but also from the continental side through the modifications of the hydrological regime.We investigate the processes controlling these coastal flooding phenomena by using hydrogeological models calibrated at large scale with an innovative method reproducing the hydrographic network. Reference study sites selected for their proven sensitivity to flooding have been used to validate the methodology and determine the influence of the different geomorphological configurations frequently encountered along the coastal line.Hydrogeological models show that the rise of the sea level induces an irregular increase in coastal aquifer saturations extending up to several kilometers inland. Back-littoral channels traditionally used as a large-scale drainage system against high tides limits the propagation of aquifer saturation upstream, provided that channels are not dominantly under maritime influence. High seepage fed by increased recharge occurring in climatic extremes may extend the vulnerable areas and further limit the effectiveness of the drainage system. Local configurations are investigated to categorize the influence of the local geological and geomorphological structures and upscale it at the regional scale.

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Impact of climate change on abstraction for hydropower and public water supply in Wales, UK

10.5194/egusphere-egu21-728 ◽

2021 ◽

Author(s):

Richard Dallison ◽

Sopan Patil

Keyword(s):

Climate Change ◽

Water Supply ◽

Hydrological Cycle ◽

Mitigation Measures ◽

Public Water Supply ◽

Worst Case ◽

Efficient Operation ◽

Substantial Impact ◽

Impact Of Climate Change ◽

The Impact

The impact of climate change on the hydrological cycle and catchment processes has been extensively studied. In Wales, such changes are projected to have a substantial impact on hydrological regimes. However, the impact on the water abstraction capability of key sectors in the country, such as hydropower (HP) and public water supply (PWS), is not yet fully understood. We use the Soil and Water Assessment Tool (SWAT) to generate future (2021-2054) daily streamflows under a worst-case scenario of greenhouse gas emissions (Representative Concentration Pathway 8.5) at two large catchments in Wales, the Conwy and Tywi. SWAT streamflow output is used to estimate the abstractable water resources, and therefore changes in the average generation characteristics for 25 run-of-river HP schemes across Conwy and Tywi and the total unmet demand for a single large PWS abstraction in the Tywi. This unmet PWS demand is assessed using the Water Evaluation And Planning (WEAP) system under increasing, static, and declining demand scenarios. Mann-Kendall trend analysis is performed to detect and characterise the trends for both sectors.Results show greater seasonality in abstraction potential through the study period, with an overall decrease in annual abstraction volume due to summer and autumn streamflow declines outweighing increases seen in winter and spring. For HP, these trends result in a projected decline in annual power generation potential, despite an increasing number of days per year that maximum permitted abstraction is reached. For PWS, under all future demand scenarios, annually there is an increase in the number of days where demand is not met as well as the total shortfall volume of water. Our results suggest that currently installed HP schemes may not make optimal use of future flows, and that the planning of future schemes should take account of these to ensure the most efficient operation is achieved. Moreover, PWS supply sustainability is under threat and will require management and mitigation measures to be implemented to ensure future supplies. Overall, our study provides a novel perspective on the future water resource availability in Wales, giving context to management planning to ensure future HP generation efficiency and PWS sustainability.

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A Practical Approach to Developing Climate Change Scenarios for Water Quality Models

Journal of Hydrometeorology ◽

10.1175/jhm-d-18-0213.1 ◽

2019 ◽

Vol 20 (6) ◽

pp. 1197-1211 ◽

Cited By ~ 4

Author(s):

Rakesh K. Gelda ◽

Rajith Mukundan ◽

Emmet M. Owens ◽

John T. Abatzoglou

Keyword(s):

Climate Change ◽

Water Quality ◽

New York ◽

Wind Speed ◽

Solar Radiation ◽

Climate Change Scenarios ◽

Quality Models ◽

Hourly Data ◽

Water Quality Models ◽

The Impact

Abstract Climate model output is often downscaled to grids of moderately high spatial resolution (~4–6-km grid cells). Such projections have been used in numerous hydrological impact assessment studies at watershed scales. However, relatively few studies have been conducted to assess the impact of climate change on the hydrodynamics and water quality in lakes and reservoirs. A potential barrier to such assessments is the need for meteorological variables at subdaily time scales that are downscaled to in situ observations to which lake and reservoir water quality models have been calibrated and validated. In this study, we describe a generalizable procedure that utilizes gridded downscaled data; applies a secondary bias-correction procedure using equidistance quantile mapping to map projections to station-based observations; and implements temporal disaggregation models to generate point-scale hourly air and dewpoint temperature, wind speed, and solar radiation for use in water quality models. The proposed approach is demonstrated for six locations within New York State: four within watersheds of the New York City water supply system and two at nearby National Weather Service stations. Disaggregation models developed using observations reproduced hourly data well at all locations, with Nash–Sutcliffe efficiency greater than 0.9 for air temperature and dewpoint, 0.4–0.6 for wind speed, and 0.7–0.9 for solar radiation.

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Future projections of river floods over the European region using EURO-CORDEX simulations

10.5194/egusphere-egu2020-15847 ◽

2020 ◽

Author(s):

Fabio Di Sante ◽

Erika Coppola ◽

Filippo Giorgi

Keyword(s):

Climate Change ◽

Hydrological Cycle ◽

Snow Accumulation ◽

Late Winter ◽

European Regions ◽

Mean Flow ◽

The North ◽

North Eastern ◽

River Floods ◽

The Impact

In a sick world with fever caused by global warming, the hydrological cycle will experience most certainly large changes in intensity and variability. One of the most intense phenomena that will probably be affected by the climate change is the flood hazard. For a long time the stakeholders have been dedicated resources to assess the risk linked to the floods magnitude and frequencies and shaping the public infrastructures based on the assumption of their immutability. Under the effect of the climate change this assumption can be broken and a different approach should be followed to avoid large disasters and threaten to the population health. In this study the biggest ever ensemble of hydroclimatic&#160; simulations has been used to simulate the river floods over the European regions. A river routing model derived from a distributed hydrological model (CHyM) has been forced with 44 EURO-CORDEX, 5 CMIP5 and 7 CMIP6 simulations to assess the effects of the climate change on the floods magnitude under two different scenarios (RCP2.6 and RCP8.5 for EURO-CORDEX and CMIP5, SSP126 and SSP585 for CMIP6). The impact of the climate change has been evaluated using a 100 year return period discharge indicator (Q100) obtained fitting a Gumbel distribution on the yearly peak discharge values. Results show a decrease of magnitude of flood events over the Mediterranean, Scandinavia and the North Eastern European regions. Over these two last regions the signal appear particularly robust and in contrast to the projected mean flow signal that is shown to increase by the end of the century mainly driven by the related increase of mean precipitations. The reduction of snow accumulation during winter time linked to a large increase of late winter temperatures is the main reason behind the decrease of floods over the North Eastern regions. An opposite signal is projected&#160; instead over Great Britain, Ireland, Northern Italy and Western Europe where a robust signal of floods magnitude increase is evident driven by e the increase of extreme precipitations. All these simulation are meant to feed the impact community and to shade the light on the use of climate information for impact assessment studies.

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Hydrological Climate-Impact Projections for the Rhine River: GCM–RCM Uncertainty and Separate Temperature and Precipitation Effects*

Journal of Hydrometeorology ◽

10.1175/jhm-d-12-098.1 ◽

2014 ◽

Vol 15 (2) ◽

pp. 697-713 ◽

Cited By ~ 24

Author(s):

Thomas Bosshard ◽

Sven Kotlarski ◽

Massimiliano Zappa ◽

Christoph Schär

Keyword(s):

Climate Change ◽

Climate Model ◽

Hydrological Cycle ◽

Regional Climate ◽

Climate Impact ◽

Rhine River ◽

Supply Source ◽

Rhine Basin ◽

Projected Changes ◽

The Impact

Abstract Climate change is expected to affect the hydrological cycle, with considerable impacts on water resources. Climate-induced changes in the hydrology of the Rhine River (Europe) are of major importance for the riparian countries, as the Rhine River is the most important European waterway, serves as a freshwater supply source, and is prone to floods and droughts. Here regional climate model data from the Ensemble-Based Predictions of Climate Changes and their Impacts (ENSEMBLES) project is used to drive the hydrological model Precipitation–Runoff–Evapotranspiration–Hydrotope (PREVAH) and to assess the impact of climate change on the hydrology in the Rhine basin. Results suggest increases in monthly mean runoff during winter and decreases in summer. At the gauge Cologne and for the period 2070–99 under the A1B scenario of the Special Report on Emissions Scenarios, projected decreases in summer vary between −9% and −40% depending on the climate model used, while increases in winter are in the range of +4% to +51%. These projected changes in mean runoff are generally consistent with earlier studies, but the derived spread in the runoff projections appears to be larger. It is demonstrated that temperature effects (e.g., through altered snow processes) dominate in the Alpine tributaries, while precipitation effects dominate in the lower portion of the Rhine basin. Analyses are also presented for selected extreme runoff indices.

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Impacts of the climate change on runoff and diffuse phosphorus load to Lake Balaton (Hungary)

Water Science & Technology ◽

10.2166/wst.2009.883 ◽

2009 ◽

Vol 59 (3) ◽

pp. 417-423 ◽

Cited By ~ 7

Author(s):

Á. Kovács ◽

A. Clement

Keyword(s):

Climate Change ◽

Hydrological Cycle ◽

Empirical Relationship ◽

Urban Runoff ◽

Weather Data ◽

Phosphorus Concentration ◽

Climate Change Scenarios ◽

Lake Balaton ◽

Phosphorus Load ◽

The Impact

The paper outlines a multi-component assessment of the impacts of the climate change on runoff and total phosphorus loads to the large shallow Lake Balaton in Hungary. Present hydrological cycle of the lake catchment has been examined using the rainfall-runoff model WetSpa. Particular phosphorus concentration in runoff was estimated on the basis of the simulated streamflow using an empirical power equation. Dissolved phosphorus concentrations were determined as a function of landuse and soil type of the corresponding sub-catchment. The model was calibrated and validated against daily observations manually at monitoring sites of sixteen inflowing streams around the lake. Runoff stemming from shoreline urban developments was calculated by the urban runoff simulation model SWMM. Phosphorus concentrations in urban runoff were calculated by an empirical relationship derived from field measurements. The model was henceforward run for climate change scenario analysis. Present weather data were modified by the climate change scenarios imported from the results of the CLIME project. The results indicate that the impact of the climate change on runoff and phosphorus load appears in the change of the distribution within a time period rather than in the total volume. However, due to the high uncertainties in climate models, the presented calculations are possible assumptions rather than established statements.

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Precipitation and temperature regime over Cyprus as a result of global climate change

Advances in Geosciences ◽

10.5194/adgeo-23-17-2010 ◽

2010 ◽

Vol 23 ◽

pp. 17-24 ◽

Cited By ~ 21

Author(s):

C. Giannakopoulos ◽

P. Hadjinicolaou ◽

E. Kostopoulou ◽

K. V. Varotsos ◽

C. Zerefos

Keyword(s):

Climate Change ◽

Global Climate Change ◽

Temperature Regime ◽

Agricultural Sector ◽

Climate Model ◽

Hydrological Cycle ◽

Global Climate ◽

Precipitation Regime ◽

Drought Duration ◽

The Impact

Abstract. In this study, the impact of global climate change on the temperature and precipitation regime over the island of Cyprus has been investigated. The analysis is based on daily output from a regional climate model (RCM) at a high horizontal resolution (25 km) produced within the framework of the EU-funded ENSEMBLES project. The control run represents the base period 1961–1990 and is used here as reference for comparison with future predictions. Two future periods are studied, 2021–2050 and 2071–2100. For the study area and over the study period, an analysis of the changes associated with the temperature regime and the hydrological cycle, such as mean precipitation and drought duration, is presented. Variations in the mean annual and seasonal rainfall are presented. Changes in the number of hot days/warm nights as well as drought duration are also discussed. These changes should be very important to assess future possible water shortages over the island and to provide a basis for associated impacts on the agricultural sector.

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Future Climate Change Impact on the Nyabugogo Catchment Water Balance in Rwanda

Water ◽

10.3390/w13243636 ◽

2021 ◽

Vol 13 (24) ◽

pp. 3636

Author(s):

Adeline Umugwaneza ◽

Xi Chen ◽

Tie Liu ◽

Zhengyang Li ◽

Solange Uwamahoro ◽

...

Keyword(s):

Climate Change ◽

Water Resources ◽

Water Balance ◽

Surface Runoff ◽

Hydrological Cycle ◽

Swat Model ◽

Global Climate Models ◽

Future Climate Change ◽

Baseline Scenario ◽

The Impact

Droughts and floods are common in tropical regions, including Rwanda, and are likely to be aggravated by climate change. Consequently, assessing the effects of climate change on hydrological systems has become critical. The goal of this study is to analyze the impact of climate change on the water balance in the Nyabugogo catchment by downscaling 10 global climate models (GCMs) from CMIP6 using the inverse distance weighting (IDW) method. To apply climate change signals under the Shared Socioeconomic Pathways (SSPs) (low and high emission) scenarios, the Soil and Water Assessment Tool (SWAT) model was used. For the baseline scenario, the period 1950–2014 was employed, whereas the periods 2020–2050 and 2050–2100 were used for future scenario analysis. The streamflow was projected to decrease by 7.2 and 3.49% under SSP126 in the 2020–2050 and 2050–2100 periods, respectively; under SSP585, it showed a 3.26% increase in 2020–2050 and a 4.53% decrease in 2050–2100. The average annual surface runoff was projected to decrease by 11.66 (4.40)% under SSP126 in the 2020–2050 (2050–2100) period, while an increase of 3.25% in 2020–2050 and a decline of 5.42% in 2050–2100 were expected under SSP585. Climate change is expected to have an impact on the components of the hydrological cycle (such as streamflow and surface runoff). This situation may, therefore, lead to an increase in water stress, calling for the integrated management of available water resources in order to match the increasing water demand in the study area. This study’s findings could be useful for the establishment of adaptation plans to climate change, managing water resources, and water engineering.

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Trends in climatic variables and future reference evapotranspiration in Duero Valley (Spain)

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-1795-2011 ◽

2011 ◽

Vol 11 (6) ◽

pp. 1795-1805 ◽

Cited By ~ 36

Author(s):

R. Moratiel ◽

R. L. Snyder ◽

J. M. Durán ◽

A. M. Tarquis

Keyword(s):

Climate Change ◽

River Basin ◽

Reference Evapotranspiration ◽

Stomatal Resistance ◽

Dew Point ◽

Maximum Temperature ◽

Net Radiation ◽

Maximum Water ◽

June July ◽

The Impact

Abstract. The impact of climate change and its relation with evapotranspiration was evaluated in the Duero River Basin (Spain). The study shows possible future situations 50 yr from now from the reference evapotranspiration (ETo). The maximum temperature (Tmax), minimum temperature (Tmin), dew point (Td), wind speed (U) and net radiation (Rn) trends during the 1980–2009 period were obtained and extrapolated with the FAO-56 Penman-Montheith equation to estimate ETo. Changes in stomatal resistance in response to increases in CO2 were also considered. Four scenarios were done, taking the concentration of CO2 and the period analyzed (annual or monthly) into consideration. The scenarios studied showed the changes in ETo as a consequence of the annual and monthly trends in the variables Tmax, Tmin, Td, U and Rn with current and future CO2 concentrations (372 ppm and 550 ppm). The future ETo showed increases between 118 mm (11 %) and 55 mm (5 %) with respect to the current situation of the river basin at 1042 mm. The months most affected by climate change are May, June, July, August and September, which also coincide with the maximum water needs of the basin's crops.

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