In this study, results from two sets of numerical simulations are evaluated and presented; one with the land surface model IBIS forced with prescribed climate and another with the fully coupled ...atmospheric general circulation and land surface model CCM3-IBIS. The results illustrate the influence of historical and potential future deforestation on local evapotranspiration and discharge of the Amazon River system with and without atmospheric feedbacks and clarify a few important points about the impact of deforestation on the Amazon River. In the absence of a continental scale precipitation change, large-scale deforestation can have a significant impact on large river systems and appears to have already done so in the Tocantins and Araguaia Rivers, where discharge has increased 25% with little change in precipitation. However, with extensive deforestation (e.g. >30% of the Amazon basin) atmospheric feedbacks, brought about by differences in the physical structure of the crops and pasture replacing natural vegetation, cause water balance changes of the same order of magnitude as the changes due to local land surface processes, but of opposite sign. Additionally, changes in the water balance caused by atmospheric feedbacks are not limited to those basins where deforestation has occurred but are spread unevenly throughout the entire Amazon by atmospheric circulation. As a result, changes to discharge and aquatic environments with future deforestation of the Amazon will likely be significant and a complex function of how much vegetation has been removed from that particular watershed and how much has been removed from the entire Amazon Basin.
The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer of 2015 was characterized by ...exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C higher than the seasonal mean (1971–2000) over most of western Europe, and more than 3 °C higher in the east. It was the hottest and climatologically driest summer over the 1950–2015 study period for an area stretching from the eastern Czech Republic to Ukraine. For Europe, as a whole, it is among the six hottest and driest summers since 1950. High evapotranspiration rates combined with a lack of precipitation affected soil moisture and vegetation and led to record low river flows in several major rivers, even beyond the drought-hit region. The 2015 drought developed rather rapidly over the Iberian Peninsula, France, southern Benelux and central Germany in May and reached peak intensity and spatial extent by August, affecting especially the eastern part of Europe. Over the summer period, there were four heat wave episodes, all associated with persistent blocking events. Upper-level atmospheric circulation over Europe was characterized by positive 500 hPa geopotential height anomalies flanked by a large negative anomaly to the north and west (i.e., over the central North Atlantic Ocean extending to northern Fennoscandia) and another center of positive geopotential height anomalies over Greenland and northern Canada. Simultaneously, the summer sea surface temperatures (SSTs) were characterized by large negative anomalies in the central North Atlantic Ocean and large positive anomalies in the Mediterranean basin. Composite analysis shows that the western Mediterranean SST is strongly related to the occurrence of dry and hot summers over the last 66 years (especially over the eastern part of Europe). The lagged relationship between the Mediterranean SST and summer drought conditions established in this study can provide valuable skill for the prediction of drought conditions over Europe on interannual to decadal timescales.
Hydrometeorological impacts due to urbanization for cities close to complex terrain are poorly understood due to the complexities of terrain‐related circulation and urban perturbations of atmospheric ...flow. In this study, we examine urban impacts on extreme monsoon rainfall and the resultant flooding over central Arizona based on high‐resolution atmospheric and hydrological model simulations. Strong positive rainfall anomalies at the urban‐rural interface downwind of the city are mainly related to dynamic effects (increased surface roughness) on convective outflow boundaries. Urban‐related thermodynamic disturbances slightly increase rain rates over the downtown core of Phoenix. Contrasting rainfall anomalies for two consecutive storm episodes highlight the importance of flow regime analysis in understanding urban impacts on extreme rainfall in complex terrain. Urban‐induced rainfall anomalies result in amplification of flood peak magnitudes by as much as a factor of 2 for Phoenix watersheds. Our results highlight the urban impacts on regional flood hydrology through land‐atmosphere interactions.
Key Points
Contrasting rainfall anomalies for two consecutive storm episodes in the Phoenix metropolitan region show a strong dependence on flow regime
The dynamic perturbation to terrain‐related circulations dominates urban‐induced rainfall anomalies in complex terrain
The impacts of urban‐induced rainfall anomalies on flood response are assessed through hydrological modeling experiments
There is increasing consensus in the hydrologic literature that an appropriate framework for streamflow forecasting and simulation should include explicit recognition of forcing and parameter and ...model structural error. This paper presents a novel Markov chain Monte Carlo (MCMC) sampler, entitled differential evolution adaptive Metropolis (DREAM), that is especially designed to efficiently estimate the posterior probability density function of hydrologic model parameters in complex, high‐dimensional sampling problems. This MCMC scheme adaptively updates the scale and orientation of the proposal distribution during sampling and maintains detailed balance and ergodicity. It is then demonstrated how DREAM can be used to analyze forcing data error during watershed model calibration using a five‐parameter rainfall‐runoff model with streamflow data from two different catchments. Explicit treatment of precipitation error during hydrologic model calibration not only results in prediction uncertainty bounds that are more appropriate but also significantly alters the posterior distribution of the watershed model parameters. This has significant implications for regionalization studies. The approach also provides important new ways to estimate areal average watershed precipitation, information that is of utmost importance for testing hydrologic theory, diagnosing structural errors in models, and appropriately benchmarking rainfall measurement devices.
•Flash floods and debris flows escape conventional hydrometeorological monitoring.•Further development of radar-based rainfall estimation and nowcasting in complex orography is key.•Effective risk ...management requires consolidating physical and social datasets of these events.•Further research should focus on methods for multiple-hazard warning.
Flash floods and debris flows develop at space and time scales that conventional observation systems for rainfall, streamflow and sediment discharge are not able to monitor. Consequently, the atmospheric, hydrological and geomorphic controls on these hydrogeomorphic processes are poorly understood, leading to highly uncertain warning and risk management. On the other hand, remote sensing of precipitation and numerical weather predictions have become the basis of several flood forecasting systems, enabling increasingly accurate detection of hazardous events. The objective of this paper is to provide a review on current European and international research on early warning systems for flash floods and debris flows. We expand upon these themes by identifying: (a) the state of the art; (b) knowledge gaps; and (c) suggested research directions to advance warning capabilities for extreme hydrogeomorphic processes. We also suggest three areas in which advancements in science will have immediate and important practical consequence, namely development of rainfall estimation and nowcasting schemes suited to the specific space–time scales, consolidating physical, engineering and social datasets of flash floods and debris-flows, integration of methods for multiple hydrogeomorphic hazard warning.
Wetlands provide numerous ecosystem services to the environment, such as nutrient removal and storage. The aim of this work is to evaluate the nutrient dynamics in different sectors within wetland ...systems in the south of the Samborombón Bay (Argentina) based on hydrological and/or anthropogenic variations. For this purpose, the hydrological features of the wetland were defined through the analysis of satellite images, precipitation and tidal data, and field surveys. Three sectors were identified in the wetland: one with tidal influence, another which is dependent on rainfall, and another that receives inputs from rainfall and from a sewage effluent treatment plant. In order to analyze the nutrient dynamics, samples of surface water, groundwater, and sediments were collected from these sectors. Measurements of pH and electrical conductivity were determined in situ in water samples, while the concentration of inorganic forms of phosphorus and nitrogen, soluble reactive silica, and organic carbon were determined through laboratory analysis. Also, bioavailable phosphorus, organic matter, pH, and electrical conductivity were determined in the sediment samples collected. Statistical analysis of the data reveals differences between the sectors and allows the interpretation of the dynamics of the studied components in the wetland. Electrical conductivity distinguishes the intertidal sectors of the wetland while components associated with P and N discriminate the sectors with inputs from the sewage effluent treatment plant. On the other hand, soluble reactive silica, organic carbon, and organic matter do not seem to be influenced by the tide or effluent discharge. This study demonstrates that the studied wetland works as a nutrient retention area, providing ecosystem services to local inhabitants. Although these services can be utilized, they require a continuous monitoring over time to provide an early warning in case the variations in P and N cycles could lead to eutrophication or wetland degradation.
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•Nutrient dynamics depend on hydrological and/or anthropogenic variations.•Tidal and non-tidal sites are discriminated by salinity in Samborombón Bay wetland.•Some non-tidal sectors receive contributions from sewage treatment plants.•P and N components may differentiate the sectors with sewage contributions.•SR silica, OC, and OM contents are not determined by the tide or effluent discharge.
•Drought in Play facilitates comprehension of drought planning concepts and principles.•Fun, engaging, and accessible approach to promote equitable water resources management.•Playful approach to ...grasp interplay between hydrological and social dynamics.•Simulate impacts of planned and unplanned actions in drought crises.•Facilitate consideration of multiple uses when developing drought plans.
Drought management requires a proactive approach and active involvement of stakeholders to enhance effectiveness and equity. However, there are challenges such as power imbalances and knowledge disparities. This paper proposes an innovative methodological tool to facilitate the understanding of key concepts, such as drought states and reservoir zoning, alerts for changes in drought state, risk predisposition, breaking down hierarchical structures of teaching and learning, contributing to more horizontal and participatory processes. We present “Drought in Play” from its creation and design to its application in two water systems in the state of Ceará, located in the Northeast region of Brazil. The game encourages active participation in the creation of a proactive drought plan for water systems and stimulates critical thought and proactive actions regarding drought and water resources management. The game was designed for a multidisciplinary team and tested with researchers that know the drought plans methodology and the challenges to build an effective drought plan. “Drought in Play’’ includes game elements (cards, boardgame) and simulations. We explore the participants’ perceptions when using this tool to facilitate stakeholder participation in building a proactive plan to deal with drought and to enable water users to collectively manage a reservoir that is a common resource to all of them. The results suggest that ”Drought in Play“ can be used as a tool for socio-hydrological modeling, because it combines hydrological elements with social aspects such as decision-making, cooperation, and conflicts among participants. The game has potential to facilitate sustainable water resources management, enhance social learning, and provide a knowledge framework to address complex environmental challenges. It can be easily adapted to other regions with similar situations without requiring further modifications.
Recently available hydrological data from Hukou station at the junction of the Poyang Lake with the Yangtze River along with other data from stations in the Poyang Lake basin have allowed further ...examination and understanding of the basin effect (basin discharge generated by rainfall) and the Yangtze River blocking effect on variations of the Poyang Lake level and floods at annual to decadal scales. Major results show that the basin effect has played a primary role influencing the level of Poyang Lake and development of severe floods, while the Yangtze River played a complementary role of blocking outflows from the lake. In most cases, only when the basin effect weakened did the river effect become large, a relationship indicating that the river’s blocking effect diminishes when the lake level is high from receiving large amount of basin discharge, albeit a few exceptions to this relationship occurred when river flow also was elevated from receiving large rainfall discharges in upstream areas. Moreover, the basin effect has become stronger in the period 1960–2003 in accordance with the increase of warm season rainfall in the Poyang Lake basin. In particular, large increases of the basin’s rainfall in the 1990s corresponded to the most severe floods (in 1998, 1995, and 1992) of the last 4 decades. The strong increase of warm season rainfall in the Poyang Lake basin in the 1990s is consistent with the recent southward shift of major warm season rain bands in eastern China. Results of this study provide a utility for improving predictions of the Poyang Lake level and floods, which affect a population of about 10 million.
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