Plastics can be used more sustainably in agriculture

Plastics have become an integral component in agricultural production as mulch films, nets, storage bins and in many other applications, but their widespread use has led to the accumulation of large quantities in soils. Rational use and reduction, collection, reuse, and innovative recycling are key measures to curb plastic pollution from agriculture. Plastics that cannot be collected after use must be biodegradable in an environmentally benign manner. Harmful plastic additives must be replaced with safer alternatives to reduce toxicity burdens and included in the ongoing negotiations surrounding the United Nations Plastics Treaty. Although full substitution of plastics is currently not possible without increasing the overall environmental footprint and jeopardizing food security, alternatives with smaller environmental impacts should be used and endorsed within a clear socio-economic framework. Better monitoring and reporting, technical innovation, education and training, and social and economic incentives are imperative to promote more sustainable use of plastics in agriculture

Temporal and depth variation of water quality due to thermal stratification in Karkheh Reservoir, Iran

Study region: Karkheh Dam Reservoir (KDR) located in western Iran. Study focus: To date, there has been no research in the KDR that investigates the interconnections among thermal stratification (ThS), water quality, and nutrients, based on field measurements. This study explored the temporal trend of ThS in the KDR and its interrelationship with water quality parameters based on data measured from 2005–2006. New hydrological insights for the region: The results showed that a noticeable ThS in the KDR starts in late April and continues until early December. The strongest ThS occurs during late summer when the water temperature difference between the surface and bottom layers in the reservoir exceeds 18 °C. As a result of external forces that generally intensify in December, vertical water circulation occurs, and by January and February there is a minimal temperature gradient between the surface and bottom layers. During ThS, dissolved oxygen (DO) is strongly confined by the metalimnion and does not penetrate into the hypolimnion. However, even during late December to February, there is a large difference between DO concentration in the surface and bottom layers, which indicates limited mixing. Ammonium increasing and nitrate decreasing with depth was observed, likely due to denitrification (in the bottom layers) and nitrification (in the surface layers), respectively. The results of the present study provide new information on the spatio-temporal variation of water quality in large reservoirs, which is important for stakeholders with concerns related to lake and reservoir eutrophication and water quality issues

Regionalization of flood magnitudes using the ecological attributes of watersheds

Estimating flood discharge at ungauged sites is a significant challenge facing water resources planners and engineers during the planning and design of hydraulic structures, managing flood prone zones, and operating artificial waterbodies. Developing more robust models to improve the reliability of flood discharge estimations is thus very useful. The role of ecological attributes including land use/land cover (LULC), hydrologic soil groups (HSG), and watershed physical characteristics (area, main stream length, average slope), and watershed shape coefficients (form, compactness, circularity, and elongation) in explaining the overall variation in flood magnitude in 39 watersheds, located in the southern basin of the Caspian Sea, was investigated. As the LULC and HSG were found to play a significant role in explaining total variation (40–89%) in flood magnitudes, their inclusion in the estimation of flood magnitudes can provide more reliable estimates of flood risk and magnitude

A critical review on the application of the National Sanitation Foundation Water Quality Index

Many studies have employed the National Sanitation Foundation Water Quality Index (NSFWQI) with non-original rather than originally defined parameters of the model, particularly when incorporating fecal coliform (FC), total solids, and total phosphates as inputs. For this reason, this study aimed to perform a critical review on the application of the NSFWQI to explore the amount of change that can be expected when users employed non-original parameters (such as orthophosphate and total dissolved solids/total suspended solids instead of total phosphorous and total solids, respectively), or different units (FC based on the maximum probable number (FC-MPN) rather than the colony forming unit (FC-CPU)). To demonstrate the influence of originally defined inputs on NSFWQI results, various scenarios were investigated. These scenarios were generated using different possible inputs to the NSFWQI, altering the FC, total solids, and total phosphorous parameters obtained from the monitoring stations of the Sefidroud River in Iran. Considerable differences were observed in the NSFWQI values when using orthophosphate and total suspended solids, instead of the originally defined data (i.e., total phosphorous and total solids), in the model (first scenario). In this case, the number of stations with “good” water quality increased from one to seven when compared with the first scenario results. In addition, unlike the results of the first scenario, none of the stations were classified as class IV (i.e., “bad” water quality status). However, the results of the implemented scenarios presented a more favorable water quality status than those obtained using the first scenario (except the second scenario which included FC-MPN rather than FC-CFU). Using total dissolved solids instead of total solids and FC-MPN rather than FC-CPU, resulted in fewer changes. In both cases, the average of the NSFWQI values in the river classed all stations as “medium” and “bad” water quality for the wet and dry seasons, respectively. Proper application of NSFWQI is important to provide high quality results for evaluation of water bodies, particularly when incorporating total solids and total phosphorous as inputs. The findings showed substantial changes in NSFWQI results when using orthophosphate and total suspended solids instead of total phosphorous and total solids, respectively. Using total dissolved solids instead of total solids and FC-MPN rather than FC-CPU, resulted in fewer changes. Generally, results indicated that the river water quality status in the wet season was better than during the dry season so that none of the scenarios classified the river water quality as “bad” (in terms of water quality status) in the wet season. Meanwhile, the river water quality was classified as “bad” for three scenarios in the dry season

Comparative assessment of spatiotemporal snow cover changes and hydrological behavior of the Gilgit, Astore and Hunza River basins (Hindukush–Karakoram–Himalaya region, Pakistan)

International audienc

Process-Constrained Statistical Modeling of Sediment Yield

Sediment transport is a major contributor to a non-point source of pollution impacted by various factors that are modulated by climatic changes and anthropogenic influences. Quantifying and disentangling the contribution of these factors to sediment yield at large scales and across different flow regimes has not been fully explored. Here we present a framework to fine-tune a stochastic sediment yield model by classifying discharge and Suspended Sediment Load (SSL) observations based on the underlying governing processes in unregulated streams with various hydrological regimes. This stochastic model, rooted in copula theory, constructs a joint distribution between discharge and SSL storm events using historical time series of observations, classified based on seasonality, hysteresis patterns, and hydrograph components of the sediment transport processes. We include hydrological, land use, and geological properties of the watersheds to describe and discuss the effects of different factors on applying the underlying dynamics to enhance sediment yield estimation/prediction accuracy. We evaluated the proposed method on 67 streams across the United States. Our results show significant improvements in sediment yield modeling performance

Relationship between water quality and macro-scale parameters (land use, erosion, geology, and population density) in the Siminehrood River Basin

To date, few studies have investigated the simultaneous effects of macro-scale parameters (MSPs) such as land use, population density, geology, and erosion layers on micro-scale water quality variables (MSWQVs). This research focused on an evaluation of the relationship between MSPs and MSWQVs in the Siminehrood River Basin, Iran. In addition, we investigated the importance of water particle travel time (hydrological distance) on this relationship. The MSWQVs included 13 physicochemical and biochemical parameters observed at 15 stations during three seasons. Primary screening was performed by utilizing three multivariate statistical analyses (Pearson's correlation, cluster and discriminant analyses) in seven series of observed data. These series included three separate seasonal data, three two-season data, and aggregated three-season data for investigation of relationships between MSPs and MSWQVs. Coupled data (pairs of MSWQVs and MSPs) repeated in at least two out of three statistical analyses were selected for final screening. The primary screening results demonstrated significant relationships between land use and phosphorus, total solids and turbidity, erosion levels and electrical conductivity, and erosion and total solids. Furthermore, water particle travel time effects were considered through three geographical pattern definitions of distance for each MSP by using two weighting methods. To find effective MSP factors on MSWQVs, a multivariate linear regression analysis was employed. Then, preliminary equations that estimated MSWQVs were developed. The preliminary equations were modified to adaptive equations to obtain the final models. The final models indicated that a new metric, referred to as hydrological distance, provided better MSWQV estimation and water quality prediction compared to the National Sanitation Foundation Water Quality Index

Spatio-temporal snow cover change and hydrological characteristics of the Astore, Gilgit and Hunza river basins (western Himalayas, Hindukush and Karakoram region) - Northern Pakistan

International audienceA large proportion of Pakistan's irrigation water supply is drawn from the Upper Indus River Basin (UIB) situated in the Himalaya-Karakoram-Hindukush (HKH) ranges. More than half of the annual flow in the UIB is contributed by five of its high-altitude snow and glacier-fed sub-basins including the Astore (Western Himalaya - southern part of the UIB), Gilgit (Hindukush - western part of the UIB) and Hunza (Central Karakoram - northern part of the UIB) River basins. Studying the snow cover, its spatio-temporal evolution and the hydrological response of these sub-basins is important so as to better manage water resources. This study compares data from the Astore, Gilgit and Hunza River basins (mean catchment elevation, 4100, 4250 and 4650 m ASL, respectively), obtained using MODIS satellite snow cover images. The hydrological regime of these sub-catchments was analyzed using hydrological and climate data available at different altitudes from the basin areas. The results suggest that the UIB is a region undergoing a stable or slightly increasing trend of snow cover in the southern (Western Himalayas), western (Hindukush) and northern (Central Karakoram) parts. Discharge from the UIB is a combination of snow and glacier melt with rainfall-runoff in the southern part, but snow and glacier melt is dominant in the northern and western parts of the catchment. Despite similar snow cover trends (stable or slightly increasing), different river flow trends (increasing in Astore and Gilgit, decreasing in Hunza) suggest that a sub-catchment level study of the UIB is needed to understand thoroughly its hydrological behavior for better flood forecasting and water resources management and to quantify how the system is being forced by changing climate