Papers by Roser Casas-Mulet
Frontiers in Environmental Science, Mar 13, 2023
River Research and Applications, Jan 10, 2023
<p>Hydropeaking has received increasing attention in the last years, but many knowl... more <p>Hydropeaking has received increasing attention in the last years, but many knowledge gaps remain, potentially hampering effective policy and management efforts in rivers under such type of hydropower production. In this study, we collected open hydropeaking research questions from over 200 experts in river science, practice, and policy across the globe using an online survey available in five languages. We used a systematic method of determining expert consensus (Delphi method) to identify 100 core questions related to the following thematic fields: (i) hydrology, (ii) physico-chemical properties of water, (iii) river morphology and sedimentology, (iv) ecology and biology, (v) socio-economics and energy markets, (vi) policy and regulation, as well as (vii) management and mitigation measures. The consensus list of questions shall inform and guide researchers in focusing their efforts to foster a better science-policy interface, thereby improving the sustainability of peak-operating hydropower in a variety of settings.</p>
<p>In light of global warming, cold water patches (CWPs) play an increasing... more <p>In light of global warming, cold water patches (CWPs) play an increasingly crucial role for the persistence of cold-adapted biological communities and the resilience of river ecosystems. Predicting the spatial distribution of CWPs is key to understanding their drivers and informing river management strategies targeting ecosystem resilience. Uncrewed Aerial Systems (UAS)-based Thermal Infra-Red (TIR) imagery technologies provides a novel tool to identify and thermally quantify CWPs at large spatial scales. When used in conjunction with optical (RGB) imagery, CWPs physical attributes and their surrounding riverscape can be characterised, allowing to assess drivers of potential thermal refugia at multiple spatial scales. However, several critical challenges in UAS-based data acquisition, processing and interpretation need to be addressed. They include: a requirement of perfect TIR-RGB overlapping during data acquisition to enable the identification and extraction of true water temperature pixels; <em>in-situ</em> stream temperature measurements to enable calibration and validation during post-processing; and the definitions of thermal and areal metric thresholds based on targeted ecological processes to identify, characterise and interpret CWPs distributions. This paper will present a set of methodological approaches used to address these challenges and obtain reliable CWPs information from UAS-based data as a basis to promote effective management of present and future freshwater ecosystems</p>
By identifying fragments of DNA in the environment, eDNA approaches present a promising tool for ... more By identifying fragments of DNA in the environment, eDNA approaches present a promising tool for monitoring biodiversity in a cost-effective way. This is particularly pertinent for countries where traditional morphological monitoring has been sparse. The first step to realising the potential of eDNA is to develop methodologies that are adapted to local conditions. Here, we test field and laboratory eDNA protocols (aqueous and sediment samples) in a range of semi-arid ecosystems in Namibia. We successfully gathered eDNA data on a broad suite of organisms at multiple trophic levels (including algae, invertebrates and bacteria) but identified two key challenges to the implementation of eDNA methods in the region: 1) high turbidity requires a tailored sampling technique and 2) identification of taxa by eDNA methods is currently constrained by a lack of reference data. We hope this work will guide the deployment of eDNA biomonitoring in the arid ecosystems of Namibia and neighbouring cou...
Water for the Environment, 2017
This chapter presents an overview of the response of water quality to hydrological alterations du... more This chapter presents an overview of the response of water quality to hydrological alterations due to anthropogenic activities and how this drives the need for environmental water provisions. The chapter outlines the major driving processes of water quality change and highlights how interactions between water quantity and quality depend on the characteristics of individual catchments and anthropogenic influences. It also discusses management strategies to mitigate some water quality problems using environmental water releases. Salinity, water temperature, nutrient concentrations, and dissolved oxygen have been selected as both representative and important indicators of stream water quality. The flow-dependent processes, anthropogenic impacts, and management options have been discussed for each of these.
<p>Increased deposition of fine sediments in streams affects a range of key ecosystem proce... more <p>Increased deposition of fine sediments in streams affects a range of key ecosystem processes across the sediment-water interface, and it is a critical aspect of river habitat degradation and restoration. Understanding the mechanisms leading to fine sediment accumulation along and across streambeds, and their affectation to ecological processes is therefore essential for comprehending human impacts on river ecosystems and inform river restoration. Here, we introduce the HydroEcoSedimentary Tool (HEST) as an integrated approach to assess hydro-sedimentary and ecologically relevant processes together. The HEST integrates the estimation of a range of processes occurring in the interstitial zone, including sedimentary (fine sediment accumulation and fine sediment loss upon retrieval), hydraulic (hydraulic conductivity), geochemical (water quality and temperature) and ecological (with a focus on brown trout early life stages).</p><p>We tested the HEST application in two rivers with different degrees of morphological degradation in Germany. The HEST was successful in recording the set of key hydrosedimentary and ecologically relevant factors, and in providing a mechanistic linkage between and biological effect in a site-specific context. The HEST data confirmed that salmonid embryo mortality could be linked to high fine deposition in gravel beds. In addition, the HEST illustrated that such mortality could be linked explicitly to interstitial depths and to different infiltration pathways for fines (e.g. vertical vs. horizontal). Although interstitial water quality and temperature were within ecological thresholds and did not show significant differences with surface water, it was still useful to monitor such variables and to rule out any effect on mortality. Water temperature, for example, could be extremely important to detect local groundwater inputs, which has been demonstrated to have a significant effect on embryo salmonids elsewhere. The HEST also allowed accounting for the loss of fines during retrieval failure and estimating hydrological factors with the HEST illustrates its additional usefulness and reliability.</p><p>Compared to other methods, the HEST expands the possibilities to monitor and quantify fine sediment deposition in streambeds by differentiating between vertical, lateral and longitudinal infiltration pathways, and distinguishing between the depth (upper vs. lower layers) at which interstitial processes occur along the streambed column.</p>
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Papers by Roser Casas-Mulet