Environmental flow assessment : an Analysis

Natural flow of a river is recognized as vital to sustaining riverine ecosystems. The biotic composition, structure and function of aquatic ecosystems depend largely on the hydrologic regimes; however flows of the world’s rivers are increasingly being modified through impoundments. Therefore calculation of the optimum flows for a healthier river is essential but there is no simple figure that can be given for the environmental flow requirements of rivers. Environmental flows refer to water for ecosystems. Ecosystems, however, provide a wide range of valuable services to people. Concept of the environmental flow was initiated not only to discover the river health and to manipulate river flow regimes, but also to get the maximum harvest from free flowing waters. Hence, providing for environmental flows is not exclusively a matter of sustaining ecosystems but also a matter of supporting human well being. As demand for freshwater continues to rise and ways are sought to improve water productivity, decision-making bodies at local, basin and national levels require accurate information on the role of river flows in sustaining a wide range of environmental benefits. For that reason assessment of environmental flows may contribute to setting management rules and monitoring their impact on river health

Drought severity–duration–frequency curves: a foundation for risk assessment and planning tool for ecosystem establishment in post-mining landscapes

Eastern Australia has considerable mineral and energy resources, with areas of high biodiversity value co-occurring over a broad range of agro-climatic environments. Lack of water is the primary abiotic stressor for (agro)ecosystems in many parts of eastern Australia. In the context of mined land rehabilitation quantifying the severity–duration–frequency (SDF) of droughts is crucial for successful ecosystem rehabilitation to overcome challenges of early vegetation establishment and long-term ecosystem resilience. The objective of this study was to quantify the SDF of short-term and long-term drought events of 11 selected locations across a broad range of agro-climatic environments in eastern Australia by using three drought indices at different timescales: the Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), and the Standardized Precipitation-Evapotranspiration Index (SPEI). Based on the indices we derived bivariate distribution functions of drought severity and duration, and estimated the recurrence intervals of drought events at different timescales. The correlation between the simple SPI and the more complex SPEI or RDI was stronger for the tropical and temperate locations than for the arid locations, indicating that SPEI or RDI can be replaced by SPI if evaporation plays a minor role for plant available water (tropics). Both short-term and long-term droughts were most severe and prolonged, and recurred most frequently in arid regions, but were relatively rare in tropical and temperate regions. Our approach is similar to intensity–duration–frequency (IDF) analyses of rainfall, which are crucial for the design of hydraulic infrastructure. In this regard, we propose to apply SDF analyses of droughts to design ecosystem components in post-mining landscapes. Together with design rainfalls, design droughts should be used to assess rehabilitation strategies and ecological management using drought recurrence intervals, thereby minimising the risk of failure of initial ecosystem establishment due to ignorance of fundamental abiotic and site-specific environmental barriers, such as flood and drought events

Monitoring of antibiotic resistance and contaminants of emerging concern in small-scale wetland-based municipal treatment systems

Human sewage is one of the major sources of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and chemical contaminants of emerging concern (CECs). Wastewater treatment is a crucial barrier to prevent environmental contamination. This study aimed to assess the efficacy of three constructed wetlands (CWs) (<200 p.e.) located in small villages, in Northern Portugal dedicated to the treatment of domestic effluents. Twenty-four hour composite samples of influent and effluent were collected over four campaigns in the winter (March), spring (May), summer (July) and autumn (October) during the year of 2023. Triplicate total DNA extracts from 50-250 ml of sample were used to measure the abundance of biomarkers associated with anthropogenic contamination (intI1; uidA; sul1; crAssphage; ermB, ermF, qacEΔ1, tetX, mefC and aph(3´´)-ib)1 and the bacterial load through 16S rRNA gene quantification by qPCR. Cultivable Escherichia coli and total coliforms were quantified on Chromogenic Coliform Agar (CCA). CECs extracted by solid-phase extraction (SPE) were quantified by liquid chromatography-mass spectrometry (LC–MS). Total coliforms ranged from 4.5 – 6.1 log UFC/mL in influent samples and 1.7 – 3.8 log UFC/mL in effluent samples. Total bacterial abundance, assessed based on the 16S rRNA gene, ranged between 8.0 – 8.9 log-units gene copy/mL in influent and 6.3 – 7.6 log-units in effluent. The biomarkers tested showed removal values of up to 3 log-units gene copy/mL. The chemical analysis of 119 compounds showed that pain killers as acetaminophen, illicit drugs as cocaine, antihyperlipidemic as fenofibric-acid, antihypertensives as irbesartan or psychoactive drugs as oxazepam were present in all samples (1st and 2nd campaigns), persisting after treatment. The results obtained so far suggest that the three CWs have good treatment capacity, with an important role of macrophytes, although dependent on the growth stage along the year, and with limited capacity to remove CECs.info:eu-repo/semantics/publishedVersio

Application of the HEC-HMS model for runoff simulation in a tropical catchment

Hydrologic simulation employing computer models has advanced rapidly and computerized models have become essential tools for understanding human influences on river flows and designing ecologically sustainable water management approaches. The HEC-HMS is a reliable model developed by the US Army Corps of Engineers that could be used for many hydrological simulations. This model is not calibrated and validated for Sri Lankan watersheds and need reliable data inputs to check the suitability of the model for the study location and purpose. Therefore, this study employed three different approaches to calibrate and validate the HEC-HMS 3.4 model to Attanagalu Oya (River) catchment and generate long term flow data for the Oya and the tributaries. Twenty year daily rainfall data from five rain gauging stations scattered within the Attanagalu Oya catchment and monthly evaporation data for the same years for the agro meteorological station Henarathgoda together with daily flow data at Dunamale from 2005 to 2010 were used in the study. GIS layers that were needed as input data for the flow simulation were prepared using Arc GIS 9.2 and used in the HEC-HMS 3.4 calibration of the Dunamale sub catchment using daily flow data from 2005 to 2007. The model was calibrated adjusting three different methods. The model parameters were changed and the model calibration was performed separately for the three selected methods, the Soil Conservation Service Curve Number loss method, the deficit constant loss method (the Snyder unit hydrograph method and the Clark unit hydrograph method) in order to determine the most suitable simulation method to the study catchment. The calibrated model was validated with a new set of rainfall and flow data (2008e2010). The flows simulated from each methods were tested statistically employing the coefficient of performance, the relative error and the residual method. The Snyder unit hydrograph method simulates flows more reliably than the Clark unit hydrograph method. As the loss method, the SCS Curve Number method does not perform well

Design droughts as planning tool for ecosystem establishment in post-mining landscapes

Eastern Australia has considerable mineral and energy resources and areas of high biodiversity value co-occurring over a broad range of agro-climatic environments. Water is the primary abiotic stressor for (agro)ecosystems in many parts of Eastern Australia. In the context of mined land rehabilitation quantifying the severity-duration-frequency (SDF) of droughts is crucial for successful ecosystem rehabilitation to overcome challenges of early vegetation establishment and long-term ecosystem resilience. The objective of this study was to quantify the SDF of short-term and long-term drought events of 11 selected locations across a broad range of agro-climatic environments in Eastern Australia by using three drought indices at different time scales: the Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), and the Standardized Precipitation-Evapotranspiration Index (SPEI). Based on the indices we derived bivariate distribution functions of drought severity and duration, and estimated the recurrence intervals of drought events at different time scales. The correlation between the simple SPI and the more complex SPEI or RDI was stronger for the tropical and temperate locations than for the arid locations, indicating that SPEI or RDI can be replaced by SPI if evaporation plays a minor role for plant available water. Both short-term and long-term droughts were most severe and prolonged, and occurred most frequently in arid regions, but were relatively rare in tropical and temperate regions. Our approach is similar to intensity-duration-frequency (IDF) analyses of rainfall crucial to design infrastructure. In this regard, we propose to apply SDF analyses of droughts to design ecosystem components in post-mining landscapes. Together with design rainfalls, design droughts should be used to assess rehabilitation strategies and ecological management based on drought recurrence intervals, thereby minimising the risk of failure of initial ecosystem establishment due to ignorance of fundamental abiotic and site-specific environmental barriers