Assessment of the impact of land use in an agricultural catchment area on water quality of lowland rivers

Spatio-temporal evolution of eutrophication and water quality in the Turawa dam reservoir, Poland

The objectives of the article are: to assess spatio-temporal evolution of eutrophication and water quality of the Turawa dam reservoir, located in south-western Poland on the Mała Panew River; to identify location and relationship between potential sources of physicochemical pollution related to the progressing process of eutrophication; and to determine trophic status and water quality indices of the selected research object. The analysis (Mann-Whitney U test, PCA, HCA, Spearman correlation matrix) showed a high susceptibility of the reservoir to eutrophication processes, especially due to the influence of dangerous loads of compounds emerging from areas with high tourist intensity and pollutants flowing from the Mała Panew River. The parameters deteriorating the ecological status were TP, DO, BOD₅, and COD. Considering the cumulative results of water quality indices for the period 1998-2020, the average water quality was in classes II or III. A noticeable deterioration appeared in water quality for the years 2016-2020, which proves the progressing eutrophication in the Turawa reservoir. In 1998-2020, the reservoir was classified as eutrophic or mesoeutrophic based on the calculated three trophic status indices. This article would help in developing a strategy for dealing with water blooms, a reliable system for monitoring pressures causing eutrophication, and optimal technologies for the reconstruction of multifunctional reservoirs.

The concept for innovative Comprehensive Assessment of Lowland Rivers

Current river assessment methods focus on evaluating a single aspect (e.g. the physical and chemical quality of the water or its hydromorphological state) and usually do not integrate various factors. The lack of an interdisciplinary method makes it difficult to correctly assess the condition of a river as a complex ecosystem significantly influenced by humans. This study aimed to develop a novel Comprehensive Assessment of Lowland Rivers (CALR) method. It is designed to integrate and evaluate all-natural and anthropopressure-related elements that influence a river. The CALR method was developed using the Analytic Hierarchy Process (AHP). The application of the AHP allowed the assessment factors to be determined and given weights to define the importance of each assessment element. As a result of AHP analyses, the following ranks were determined for the six main parts of the CALR method: hydrodynamic assessment (0.212), hydromorphological assessment (0.194), macrophyte assessment (0.192), water quality assessment (0.171), hydrological assessment (0.152) hydrotechnical structures assessment (0.081). In the comprehensive assessment of lowland rivers, each of the six elements listed above is rated on a scale of 1-5 (where 5 means very good and 1 bad) and multiplied by an appropriate weighting. After summing up the obtained results, a final value is obtained, classifying the river. CALR can be successfully applied to all lowland rivers thanks to its relatively simple methodology. The widespread use of the CALR method may facilitate the assessment process and enable the comparison of the condition of lowland rivers worldwide. The research conducted in this article is one of the first attempts to develop a comprehensive method for evaluating rivers that considers all aspects.

Assessment of Water Quality Indicators in the Orla River Nitrate Vulnerable Zone in the Context of New Threats in Poland

Currently, one of the most serious threats to the environment in rural areas is industrial livestock production, which generates a significant amount of chemical and biological pollution. It causes pollution of waters, affects biodiversity, and has an impact on the climate. Research was carried out in the Orla River (Poland) with a catchment area of 1.546 km2. Studies were concentrated on pH, dissolved oxygen, alkalinity, and other factors. Analyses were conducted on the area of livestock buildings in two buffer zones, 1 and 3 km wide, respectively, and included the abundance of phosphorus and potassium in soil as well as its potential impact on the quality of river water. Seasonal variability was observed for nutrients. In the winter period the highest concentrations of nitrates were observed, while in the summer this was the case for phosphates and total phosphorus. The highest concentrations of nutrients occurred in 2012, particularly total and ammonium nitrogen. There was a positive correlation between livestock building area and parameters such as ammonium, organic, and total nitrogen in the 1 km buffer, as well as organic and total nitrogen, potassium and dissolved oxygen in the 3 km buffer. Negative correlation in the case of pH was observed in both buffer zones. Relationships were found between the area of livestock buildings and parameters analyzed during seasons.

The Macrophyte Indices for Rivers to Assess the Ecological Conditions in the Klina River in the Republic of Kosovo

Macrophytes are important elements of aquatic ecosystems that grow in or near water. Their taxonomic composition, species diversity, depth, and density are indicators of environmental health; as such, Macrophytes are used to assess the ecological status of water bodies. Under the aim of assessing the ecological status of the Klina River in Kosovo, a survey was conducted at eight sampling sites along the river course to analyze macrophyte composition, diversity, density, and cover. Three samples were collected at each sampling site from early June to late September. The following macrophyte indices were used to assess the ecological status of the river: Macrophyte Index for Rivers (MIR), River Macrophyte Nutrient Index (RMNI), and River Macrophyte Hydraulic Index (RMHI). Our sampling area included the upper reaches of the river where no organic pollution was detected (oligotrophic), the middle reaches where polluted water from farms is discharged into the river, and the lower reaches characterized by heavy organic pollution from settlements and various industrial activities. There is a positive correlation (p < 0.05) between water temperature, turbidity, electrical conductivity (EC), total dissolved solids (TDS), orthophosphates (PO43−), ammonia (NH4+), nitrites (NO2−), calcium (Ca2+), and potassium (K+) with plant density, RMNI, RMHI, EQR-RMNI, EQR-RMHI, and MIR. Sodium (Na+) has stronger positive correlation (p < 0.01) with RMNI and RMHI indices and negative correlation with EQR-RMNI and EQR-RMHI. Our results show that ecological status along the river varies from high and good upstream to poor, bad, and moderate running downstream.

Spatiotemporal variations of surface water quality in a medium-sized river catchment (Northwestern Germany) with agricultural and urban land use over a five-year period with extremely dry summers

Medium-sized rivers, which are used for intensive agriculture and urban infrastructure, are subject to manifold hydrochemical stressors. Identifying and monitoring these stressors is important for river basin management and a functioning ecosystem. To understand the spatiotemporal variation of surface water quality in a highly modified lowland river, the Münstersche Aa River (Northwestern Germany) with 62% of land used for agriculture and 26% urban/residential area, was exemplarily studied. A total of 519 samples were collected using two automated high-frequency samplers and five catchment-wide sampling campaigns. They covered the five-year period 2015-2020 and included two extremely dry summers. The Münstersche Aa catchment is dominated by low permeable strata resulting in surface water runoff (Baseflow Index: 0.41) which leads to a high amplitude of discharge variation (mean discharge: 0.7 m³/s) with high flow conditions in winter/spring, and low discharge during summer/fall. In wintertime, maximum nitrate concentrations (up to 73 mg NO₃/L) and loads (up to 1300 t NO₃/a; up to 98% in winter) correlate with high-flow conditions. δ¹⁸O and δ¹⁵N isotopic analysis indicated manure from farmland as the major source of nitrate whereas the impact of municipal wastewater treatment plants was neglectable. Increased nitrate concentrations are linked to the higher proportion of farmland in the upper catchment (77%) compared with the lower catchment (47%). In summertime, at extremely low flow conditions, surface water consisted of up to 100% of treated wastewater, resulting in the highest measured chloride, sodium and potassium concentrations. The river is impacted by strongly seasonal and different stressors, which can be expected to intensify with ongoing climate change. Results from this study may help to adapt monitoring schemes for the Münstersche Aa but also for other lowland streams with comparable land-use targeting the goals of the Water Framework Directive.