María José Polo

Panta Rhei 2013–2015: global perspectives on hydrology, society and change

ABSTRACT In 2013, the International Association of Hydrological Sciences (IAHS) launched the hydrological decade 2013–2022 with the theme “Panta Rhei: Change in Hydrology and Society”. The decade recognizes the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions. This paper reports on the first Panta Rhei biennium 2013–2015, providing a comprehensive resource that describes the scope and direction of Panta Rhei. We bring together the knowledge of all the Panta Rhei working groups, to summarize the most pressing research questions and how the hydrological community is progressing towards those goals. We draw out interconnections between different strands of research, and reflect on the need to take a global view on hydrology in the current era of human impacts and environmental change. Finally, we look back to the six driving science questions identified at the outset of Panta Rhei, to quantify progress towards those aims. Editor D. Koutsoyiannis; Associate editor not assigned

Adaptation of water resources systems to changing society and environment: a statement by the International Association of Hydrological Sciences

ABSTRACT We explore how to address the challenges of adaptation of water resources systems under changing conditions by supporting flexible, resilient and low-regret solutions, coupled with on-going monitoring and evaluation. This will require improved understanding of the linkages between biophysical and social aspects in order to better anticipate the possible future co-evolution of water systems and society. We also present a call to enhance the dialogue and foster the actions of governments, the international scientific community, research funding agencies and additional stakeholders in order to develop effective solutions to support water resources systems adaptation. Finally, we call the scientific community to a renewed and unified effort to deliver an innovative message to stakeholders. Water science is essential to resolve the water crisis, but the effectiveness of solutions depends, inter alia, on the capability of scientists to deliver a new, coherent and technical vision for the future development of water systems. EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR not assigned

Study of Snow Dynamics at Subgrid Scale in Semiarid Environments Combining Terrestrial Photography and Data Assimilation Techniques

AbstractSnow cover simulation is a complex task in mountain regions because of its highly irregular distribution. GIS-based calculations of snowmelt–accumulation models must deal with nonnegligible scale effects below cell size, which may result in unsatisfactory predictions depending on the study scale. Terrestrial photography, whose scales can be adapted to the study problem, is a cost-effective technique, capable of reproducing snow dynamics at subgrid scale. A series of high-frequency images were combined with a mass and energy model to reproduce snow evolution at cell scale (30 m × 30 m) by means of the assimilation of the snow cover fraction observation dataset obtained from terrestrial photography in the Sierra Nevada, southern Spain. The ensemble transform Kalman filter technique is employed. The results show the convenience of adopting a selective depletion curve parameterization depending on the succession of accumulation–melting cycles in the snow season in these highly variable environments. A...

Terrestrial photography as an alternative to satellite images to study snow cover evolution at hillslope scale

In Mediterranean regions, where the water shortage is a serious and recurrent problem, it is essential to know the behaviour and evolution of the snow. Satellite remote sensing is widely used to find out the evolution of the snow cover extension at medium-large scales. But these techniques pose some constraints if snow is heterogeneously distributed, as they do not correctly represent the physical processes that occur on a smaller scale than the satellite image. In such cases, terrestrial photographs, whose resolution can be more easily adapted to the required resolution for these study cases, are an economic and also efficient alternative. This work presents a methodology for the georeferencing and automatic detection of snow in terrestrial photography, as an alternative to the use of satellite images for the study of the snow cover evolution in small areas. This methodology has been evaluated during the snowmelt period in the spring of 2009 at a study site in Sierra Nevada Natural Park (Southern Spain). The resulting snow maps have been compared with the results available for that period obtained from the analyses of four Landsat images. The results show that the use of Landsat generally overestimated the extension of the snow cover in the study area.

Copper and zinc adsorption by sewage sludge‐treated soil in southern Spain

Abstract Heavy metal accumulation in soil due to the application of sewage sludge may induce changes in its ionic retention capacity. In this work, sludge application effects on copper (Cu) and zinc (Zn) adsorption by the surface horizon of a calcareous soil in Southern Spain have been studied. Sludge from the urban waste water treatment plant in Cordoba was applied at rates of 0,40, and 80 Mg sludge ha‐1 for two consecutive years. Despite the low metal content of this sludge and the high amount of organic matter added, a decrease in the soil adsorption levels for both Cu and Zn was detected in the sludged samples. Differences were observed, though, in the behavior of each metal, relative to the main adsorption mechanism involved. Copper adsorption was related to carbonate surfaces in soil. Values up to 400 mmol adsorbed Cu kg‐1 soil were obtained for the three treatments, in equilibrium with 13.6, 16.7, and 17.4 mmol Cu m‐3 in solution for 0, 40, and 80 Mg sludge ha‐1, respectively, the first year, and 1...

Snow evolution in Sierra Nevada (Spain) from an energy balance model validated with Landsat TM data

Sierra Nevada Mountains are the highest continental altitude in Spain. Located in the South, facing the Mediterranean Sea in a distance of less than 40 km, the high level of solar energy income throughout the year, together with the extremely variable character of climate in such latitudes, make it necessary to use energy balance approaches to characterize the snow cover evolution. Wind and relative humidity become decisive factors in the evolution of the snow cover due to the high evaporation rates that can arise under favourable meteorological conditions. This work presents the enhanced capability of the combination of Landsat TM data with the simulation of an energy balance model to produce sequences of hourly high resolution maps of snow cover and depth distribution under variable meteorological conditions such as those found in Mediterranean mountainous watersheds. Despite the good agreement found between observed and predicted snow pixels, different examples of disagreement arose in the boundaries, most of them related to the temperature and wind speed spatial pattern simulation together with the discrimination between rain and snowfall occurrence.

Peaks Over Threshold (POT): A methodology for automatic threshold estimation using goodness of fit p-value

Threshold estimation in the Peaks Over Threshold (POT) method and the impact of the estimation method on the calculation of high return period quantiles and their uncertainty (or confidence intervals) are issues that are still unresolved. In the past, methods based on goodness of fit tests and EDF-statistics have yielded satisfactory results, but their use has not yet been systematized. This paper proposes a methodology for automatic threshold estimation, based on the Anderson-Darling EDF-statistic and goodness of fit test. When combined with bootstrapping techniques, this methodology can be used to quantify both the uncertainty of threshold estimation and its impact on the uncertainty of high return period quantiles. This methodology was applied to several simulated series and to four precipitation/river flow data series. The results obtained confirmed its robustness. For the measured series, the estimated thresholds corresponded to those obtained by nonautomatic methods. Moreover, even though the uncertainty of the threshold estimation was high, this did not have a significant effect on the width of the confidence intervals of high return period quantiles.

Effects of Renewable Energy Production and Infrastructure on Wildlife

The high levels of human demands of resources—from food to space and energy—are one of the main drivers of global change and are causing large negative impacts on ecosystems functioning worldwide (Vitousek et al. 1997). Global change components range from climate change to habitat destruction, species invasions, pollution and eutrophication. Although these factors can produce ecosystem changes independently, the final descent is often driven by synergistic processes. The resulting amplifying feedbacks can be disconnected from the original driver of change, leading to a state shift in the biosphere with unexpected consequences (Barnosky et al. 2012). Climate change seems to have taken prominence over other drivers of global change, leading to larger funding and attention with respect to other major components of global change (Verissimo et al. 2014).

Assessing minimum environmental flows in nonpermanent rivers

The criteria used in the computation of the minimum environmental flow regime and flow cessation periods in nonpermanent rivers are often left to open criteria. This study proposes a stochastic approach for evaluating the choice of local thresholds in the characterization of minimum environmental flows through both the Monte Carlo technique and local hydrological relationships. This approach is applied to four regimes obtained by hydrologic and hydraulic habitat modeling in a Mediterranean watershed. The operationality, defined as the probability of the calculated environmental regime being satisfied by the natural regime over 25 years, was assessed for eight different scenarios. Two monthly minimum environmental flow regimes were then generated, with 90 and 95% operationality levels. This analysis allows the generation of minimum flow regime prescriptions from a strictly hydrologic point of view. The methodology proposed constitutes a useful tool for the implementation of uncertainty analysis of environmental flows in water resource management. Minimum environmental flows are sensitive to thresholds applied in the calculations.We propose a stochastic approach for determining local thresholds.Optimization was applied to give prescriptions based on an operationality assessment.A tool for the uncertainty assessment required in risk analysis is provided.

Modelling surface energy fluxes over a dehesa ecosystem using a two-source energy balance model and medium resolution satellite data

The dehesa, the most widespread agroforest ecosystem in Europe (≈ 3 million ha), is recognized as an example of sustainable land use and for its importance in rural economy. It is characterized by widely-spaced oak trees (mostly Quercus Ilex L.), combined with crops, pasture and shrubs in the sub-canopy region. The estimation of the ecosystem evapotranspiration (ET) using remote sensing may assist the monitoring of its state from local to regional scales, improving the management and the conservation of the ecosystem. Thermal-based energy balance techniques which distinguish soil/substrate and vegetation contributions to the radiative temperature and radiation/turbulent fluxes have proven to be reliable in the estimation of the energy surface fluxes, and therefore in the estimation of ET. In particular, the two-source energy balance (TSEB) model of Norman et al. and Kustas and Norman has shown to be robust for semi-arid sparse canopy-cover landscapes. With the objective of evaluating the model over this environment, an energy flux measurement system has been used. It was installed in a dehesa located in Southern Spain (38°12′ N; 4°17′ W, 736m a.s.l) with 1 km homogeneous fetch in wind direction. The quality of the measured data fluxes has been tested with the energy-balance closure criterion yielding an average closure of 86% which is within the error range found in similar studies. The TSEB model was evaluated in the area for 2012 summer season, using images from MODIS (Moderate Resolution Imaging Spectroradiometer) sensor and ground measured meteorological data. The half-hourly estimates were compared with the flux tower measurements, obtaining a RMSD between modeled and measured energy fluxes within the closure balance error.