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Exploring the contributions of new and old water to runoff during precipitation events in agricultural catchments is essential for understanding runoff generation, solute transport, and soil erosion. The aim of this study was to investigate the variability in the isotopic composition of precipitation and runoff in the 66 ha agricultural catchment in Austria, in the Hydrological Open Air Laboratory (HOAL), in order to compare two isotope hydrograph separation methods. The classical two‐component (IHS) and the ensemble hydrograph separation (EHS) were applied to multiple large events in May–October of 2013–2018 using δ18O and δ2H. The peak flow new water contributions obtained by IHS were compared with the average new water fraction from EHS. The average new water fraction calculated with EHS based on regular weekly sampling was close to zero, which can be explained by the large diffuse groundwater discharge into the stream between the events. When only investigating events with high temporal resolution sampling, the results suggest that EHS provided average new water fractions during peak flows (0.46 ± 0.04 for δ18O, 0.47 ± 0.03 for δ2H) that were close to the averages obtained by IHS (0.47 for δ18O, 0.50 for δ2H). New water fractions tended to be higher for larger rainfall intensities. High peak flow new water fractions could be explained by the agricultural land use and soils with low permeability promoting overland flow generation and by some of the tile drainage systems contributing to the delivery of water. In conclusion, a weekly sampling frequency was not sufficient in the HOAL but instead high‐resolution sampling during events was necessary to estimate the average new water contributions during events. While EHS may be a more robust approach compared to IHS, as it relaxes some of the assumptions of IHS, IHS can provide information on the variability of new water contributions of individual events. [ABSTRACT FROM AUTHOR]

Agriculture is an essential economic activity in Brazil. However, it is also the main source of water quality degradation. Monitoring catchments with agricultural land use is a way to generate information on a scale to identify causes and sources of water quality degradation. This work used monitoring data derived from hydrology and the quality of surface and underground water in an intensive agricultural catchment in the Atlantic Forest biome. The Fortaleza River catchment is located in the western part of Santa Catarina state in southern Brazil and has 62 km2 of drainage area. Hydrological and water quality monitoring was conducted for 7 years at two fluviometric stations, three lysimeters, one meteorological station, and one piezometer. Data on precipitation, temperature, water flow, surface runoff, drainage, and water quality were used. Statistical analyses were also developed. Precipitation between 2013 and 2019 presented a homogeneous distribution in monthly and annual data, with January and July the months with the highest and lowest values, respectively. Statistical difference in the average and Q95 flows was found in upstream and downstream fluviometric sections. In terms of quality, statistical differences were identified for ammonium, nitrate, and potassium concentrations, which had higher concentrations in lysimeter runoff, indicating direct influence of agricultural activity on water quality. Principal component analysis (PCA) indicated that (i) surface water presented a positive relationship in Component 1 for the magnesium-calcium, sulphate-chloride, and acetate-bromide groups and a negative relationship for phosphate-nitrate; (ii) in lysimeters, the positive relationship occurred for Component 2 for the phosphate-chloride and sulphate-nitrate groups and was negative for ammonium-lithium and calcium-potassium-magnesium; and (iii) in piezometer, positive relationships were found for chloride-sodium and phosphate-nitrite pairs, while negative relationships were found for calcium-magnesium. [ABSTRACT FROM AUTHOR]

Mountains are diverse environments with a long history of changes in land use and land cover caused by a combination of natural environmental processes and human activity. The objective of this study was to analyse the impact of human–environment interactions over the period 1846–2019 on land use change in three catchments lying along an altitudinal gradient in the Polish Western Carpathians, placing special emphasis on forest and cultivated land as landscape units. Analysis of cadastral and topographic maps, orthophotomaps and demographic and socio-economic data indicated that environmental conditions combined with the socio-economic system had the greatest influence on land use patterns. Land use change in the Polish Western Carpathians following the introduction of a free-market economy in 1989 was probably occurring at the fastest rate in the last 200 years. Although changes in forest and cultivated land may be temporarily delayed or accelerated by local human activities, they are ultimately consistent with the longer-term trends in land use change observed in the mountains of Europe. Land use change in the catchments studied showed wide variations along the altitudinal gradient in the three different socio-economic systems—traditional capitalism, communism with a centrally planned economics and free-market economics. The greatest changes in land use in terms of area occurred in the catchment in the foothills of the Polish Carpathians. Land use and land cover stability increased with altitude and was most pronounced in the highest mountain catchment, reflecting a decrease in human settlement and consequently a decrease in land use change at higher altitudes. In contrast, the upper boundary of cultivated land and the lower boundary of forest—the highest or lowest altitude to or from which the forest or cultivated land extends—were less stable in mountain catchments than in the foothills. Similarly, the range of changes in forest dominance was wider and the occurrence of cultivated land on slopes was higher in the mountain catchments than in the foothill catchment. This underlines a faster abandonment of cultivated land on steeper slopes within higher altitude catchments, where climatic and soil conditions are less favourable for agricultural development. [ABSTRACT FROM AUTHOR]

Predicting and estimating sediment yield from the catchment is crucial for the effective management of water resources and controlling soil erosion. Until now, Universal Soil Loss Equations (USLE) and their modifications are appreciated and commonly applied among many methods. The idea of this work is to use the ESDAC database (a web platform hosting a series of pan-European and global datasets on soil erosion) to build the modified form of the USLE for the Zagożdzonka catchment, a small agricultural area located in central Poland. The calculated sediment yield is compared with the one determined based on the reservoir survey. Conducted analyses show that the average annual suspended sediment yield from the study catchment estimated using the MUSLE equation accounts for 201 Mg and is close to that determined based on the reservoir survey, i.e., 248 Mg. However, MUSLE, with the initially proposed parameters, will overpredict sediment transport at the study site. The ESDAC database may support local studies concerning soil erosion and sediment transport. The research is helpful for policymakers, planners, and engineers.

Predicting and estimating sediment yield from the catchment is crucial for the effective management of water resources and controlling soil erosion. Universal Soil Loss Equations (USLE) and their modifications have been appreciated and commonly applied among many methods. The idea of this work is to use the ESDAC database (a web platform hosting a series of pan-European and global datasets on soil erosion) to build the modified form of the USLE for the Zagożdzonka catchment, a small agricultural area located in central Poland. The calculated sediment yield is compared with the one determined based on the reservoir survey. The conducted analyses show that the average annual suspended sediment yield from the study catchment estimated using the MUSLE equation accounts for 201 Mg and is close to that determined based on the reservoir survey, i.e., 248 Mg. However, MUSLE, with the initially proposed parameters, will overpredict sediment transport at the study site. The ESDAC database may support local studies concerning soil erosion and sediment transport. The research is helpful for policymakers, planners, and engineers. [ABSTRACT FROM AUTHOR]

The Ca River basin has an area of 27,200 km2 distributed across the territories of two countries: Vietnam (65.2%) and Lao (34.8%). Spatial and temporal variations in suspended sediment (SS) and dissolved nutrients (PO43-, NO3-, SiO2) were determined in two hydrological stations located along the Ca River 4–6 times per month in the rainy season and 1–4 times per month in the dry season, between the months of August 2017 and July 2018. A loading–discharge (L–Q) curve was used to analyze the correlation among water physicochemical parameters with seasonal river discharge. The results indicate that SS was higher in upstream flows compared to downstream flows, which is primarily due to erosion. Seasonal SS and dissolved phosphate have an inverse correlation trend to that of dissolved silica. Results revealed that the concentration of phosphate and SS was higher in the rainy season than in the dry season. This finding proves that rain washes particulate matter from the surface runoff into the Ca River. Significant correlations between discharge and dissolved nutrient load were observed. This study provides useful information regarding variations of SS and water physicochemical parameters with seasonal water discharge in the Ca River. HIGHLIGHTS Quartz is the predominant mineral in the SS samples.; SS concentrations were higher in upstream flows compared to downstream flows.; A positive correlation between discharge and the dissolved nutrient load was shown.; The strong influence of topography and agricultural land on nutrient levels in the Ca River.; Dilution or chemostatic behavior occurs at a discharge rate of more than 500 m3/s.;

Nitrate stable isotopes provide information about nitrate contamination and cycling by microbial processes. The Fischa-Dagnitz (Austria) spring and river system in the agricultural catchment of the Vienna basin shows minor annual variance in nitrate concentrations. We measured nitrate isotopes (δ15N, δ18O) in the source spring and river up to the confluence with the Danube River (2019–2020) with chemical and water isotopes to assess mixing and nitrate transformation processes. The Fischa-Dagnitz spring showed almost stable nitrate concentration (3.3 ± 1.0 mg/l as NO3–-N) year-round but surprisingly variable δ15N, δ18O-NO3– values ranging from +5.5 to +11.1‰ and from +0.5 to +8.1‰, respectively. The higher nitrate isotope values in summer were attributed to release of older denitrified water from the spring whose isotope signal was dampened downstream by mixing. A mixing model suggested denitrified groundwater contributed > 50 % of spring discharge at baseflow conditions. The isotopic composition of NO3– in the gaining streams was partly controlled by nitrification during autumn and winter months and assimilation during the growing season resulting in low and high δ15N-NO3– values, respectively. NO3– isotope variation helped disentangle denitrified groundwater inputs and biochemical cycling processes despite minor variation of NO3– concentration. [ABSTRACT FROM AUTHOR]

Landscape discretization is an essential hydrological modeling pre-processing step that comprises the numerical representation of different geographical objects considered in the modeling process and the connections between these objects within a graph structure. GROOV'Scape is a new landscape discretization procedure that (i) produces an oriented tree of a wide range of human-made landscape elements, such as plots, hedges, benches, grass stripes, and ditches, (ii) is fully automated to avoid local drainage anomalies that require user corrections, and (iii) is fast enough to enable sensitivity analysis and the interactive production of mediated modeling landscape management scenarios. GROOV'Scape was tested on a small agricultural catchment in south-west France (Doazit catchment, 9.05 km2). The results show good agreement between the connections of areal units computed by GROOV'Scape and those observed in the field. The system exhibited substantial sensitivity to the user's choice of minimum area unit size and of digital elevation model (DEM) resolution, suggesting trial-and-error approaches are needed to reach the best landscape discretization for any given modeling purpose. Finally, we demonstrated the feasibility of using GROOV'Scape to find an optimum configuration of an infrastructure network with respect to a given ecosystem function. HIGHLIGHTS GROOV'Scape produces an oriented tree of human-made landscape elements.; Fully automated and fast for sensitivity analysis and exploration of scenarios.; Good agreement of GROOV'Scape-oriented trees with field observations.; Trial-and-error approaches are needed to reach the best landscape discretization.; GROOV'Scape helps to find an optimum configuration of an infrastructure network.;

• Identification of N and P concentration extremes using Extreme Value Theory. • High rainfall intensities after droughts led to P concentration maxima and N concentration minima. • Infiltration-excess overland flow and erosion as main P export mechanisms during extreme events. • Potentially large ecological impacts due to occurrence in the low-flow season. The profound influence of climate change on the hydrological cycle raises concerns about its potential impacts on water quality, particularly in agricultural catchments. Here, we analysed 200 storm events monitored for nitrate and total phosphorus (TP) at sub-hourly intervals from 2016 to 2023 in the Kervidy-Naizin catchment (north-western France). Using Extreme Value theory, we identified storm events with extreme concentrations and compared their hydroclimatic characteristics to those of non-extreme events. We hypothesised that extreme concentration events occurred under extreme hydroclimatic conditions, which are projected to become more frequent in the future. The extreme events identified showed dilution patterns for nitrate, with concentrations decreasing by up to 41 %, and accretion patterns for TP, with concentrations increasing by up to 1400 % compared to non-extreme events. Hydroclimatic conditions during extreme concentration events were characterised by high rainfall intensities and low antecedent discharge, but no particular conditions for mean discharge. During non-extreme events, nitrate concentration-discharge relationships exhibited primarily clockwise hysteresis, whereas TP displayed an equal mix of clockwise and anticlockwise loops. In contrast, extreme events showed more anticlockwise hysteresis for nitrate and weak hysteresis for TP. We interpreted these dynamics and their hydroclimatic controls as the result of infiltration-excess overland flow diluting nitrate-rich groundwater and exporting large amounts of TP during intensive rainfall events following droughts, while groundwater fluctuations in the riparian zone and streambed remobilization control nutrient exports during non-extreme events. Given the increasing frequency and intensity of hydroclimatic extremes, such retrospective analyses can provide valuable insights into future nutrient dynamics in streams draining agricultural catchments. [Display omitted] [ABSTRACT FROM AUTHOR]

The studies of micromycetes fungi and physicochemical properties were carried out on the soils of buffer zones of a small watercourse in the agricultural landscape of north-eastern Poland. One of the zones was under a tree which was adjacent to the arable soil, the other one was under a turf located near the grassland. It turned out that the character of vegetation and the way the land was used had an influence on the analysed soil parameters. Soil under trees was characterized by more diversified structures of fungi communities, it also produced more carbon dioxide and nitrous oxide than soil under turf. This allows us to state that tree-lined buffer zones are more effective in preventing surface water pollution by biogenic compounds displaced from agricultural land compared to the buffer zone under the grassing.

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. [ABSTRACT FROM AUTHOR]

The rivers of agricultural catchment areas are particularly vulnerable to eutrophication, which causes nitrate nitrogen (N-NO3) that can be easily leached from the cropland. In 1991, the EU implemented the Nitrates Directive (ND) to identify and reduce the negative effects of nitrates in water. According to this regulation, in 2018, the whole territory of Poland was classified as Nitrate Vulnerable Zone (NVZ). The aim of the study was to assess the validity of the introduction of NVZs in large areas of the river catchment level. Statistical data on agricultural changes for individual provinces of Poland and for the whole country were analyzed. A one-way analysis of variance (ANOVA) was used to assess the N-NO3 content in the water at different locations along the river within four rivers in the Odra basin. The results indicated that higher concentrations are observed in the upper part of the studied catchments, which reached a maximum of 25.0 mg N-NO3·dm−3. However, average values rarely exceeded 11.3 mg N-NO3·dm−3, the limit according to the Nitrates Directive. The large variability in N-NO3 content suggests the need to redefine the actual NVZs since it is essential for the appropriate implementation of programs aimed at restoring water quality according to ND. [ABSTRACT FROM AUTHOR]

The studies of micromycetes fungi and physicochemical properties were carried out on the soils of buffer zones of a small watercourse in the agricultural landscape of north-eastern Poland. One of the zones was under a tree which was adjacent to the arable soil, the other one was under a turf located near the grassland. It turned out that the character of vegetation and the way the land was used had an influence on the analyzed soil parameters. Soil under trees was characterized by more diversified structures of fungi communities, it also produced more carbon dioxide and nitrous oxide than soil under turf. This allows us to state that tree-lined buffer zones are more effective in preventing surface water pollution by biogenic compounds displaced from agricultural land compared to the buffer zone under the grassing. [ABSTRACT FROM AUTHOR]

Climate change and agricultural intensification are expected to increase soil erosion and sediment production from arable land in many regions. However, so far, most studies have been based on short-term monitoring and/or modeling, making it difficult to assess their reliability in terms of long-term changes. We present the results from a unique data set consisting of measurements of sediment loads from a 60ha catchment (the HOAL Petzenkirchen in Austria) over a time window spanning 72 years. Specifically, we compare Period I (1946-1954) and Period II (2002-2017) by fitting sediment rating curves for the growth and dormant seasons for each of the periods. The results suggest a significant increase in sediment yield from Period I to Period II with an average of 11.6±10⋅8 ton.yr-1 to 63.6±84.0 ton⋅yr-1. The sediment flux changed mainly due to a shift of the sediment rating curves (SRC), given that the annual streamflow varied little between the periods (5.6 l.s-1 and 7.6 l.s-1, respectively, on average). The slopes of the log regression lines of the SRC for the growing season and the dormant season of Period I were 16.72 and 4.9, respectively, whilst they were 5.38 and 1.17 for Period II, respectively. Climate change, considered in terms of rainfall erosivity, was not responsible for this shift, given that erosivity decreased by 30.4% from the dormant season of Period I to that of Period II, and no significant difference was found between the growing seasons of Periods I and II. However, the sediment flux changes can be explained by changes in crop type and parcel structure. During low and median streamflow conditions (i.e. Q < Q20%), land consolidation in Period II (i.e. theparcel effect) did not exert an apparent influence on sediment production. Whilst with increasing stream flow (Q > Q20%), parcel structure played an increasingly role in sediment yield contribution, and leading to a dominant role due to enhanced sediment connectivity in the landscape at extremely high flow conditions (i.e. Q > Q2%). The increase in cropland in Period II at the expense of grassland had an unfavourable effect on sediment flux, independent of streamflow, with declining relevance as flow increased. We conclude that both land cover change and land consolidation should be accounted for simultaneously when assessing sediment flux changes. Especially during extremely high flow conditions, land consolidation substantially alters sediment fluxes, which is most relevant for long-term sediment loads and land degradation. Increased attention to improving parcel structure is therefore needed in climate adaptation and agricultural catchment management. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the content of soluble forms of fertilizer nutrients (N, P, K) in the cultivated soil layer up to 20 cm deep from agricultural land in the river valley, and the concentration of these nutrients in the surface waters of the Raszynka River.

The 8‐km2 Morcille catchment, which is a sub‐catchment of the 150‐km2 Ardières catchment in the Beaujolais region of France, is one of the first sites in Europe where research has been conducted on surface water contamination by pesticides. A consolidated hydrological and chemical dataset has been set up with data collected since 2002 on the Morcille River and since 2011 on the Ardières River. Additional data on the ecotoxicological and ecological impacts of pesticides on aquatic microbial communities and macroinvertebrates has also been recorded in both rivers since 2005. The 'Site Atelier Ardières‐Morcille Dataset' described here combines rainfall and stream water height measurements at gauged stations with concentrations of two trace elements and nine pesticides (mainly herbicides, fungicides and some of their metabolites) in both the Ardières and Morcille rivers. All contaminant concentration data showed spatial and temporal variability in water quality associated with pesticide use and rainfall patterns. This long‐term monitoring framework made it possible to estimate the persistence of two herbicides (diuron and norflurazon) after legislation banning them. It took 4 years for diuron and more than 10 years for norflurazon concentrations to fall below 0.1 μg/L. Concurrent biological data showed a gradient of impacts consistent with chemical anthropogenic pressure, and rapid recovery of phototrophic microbial communities after the diuron ban. Finally, monitoring data on pesticide transport in a grassed strip set on a slope of the Morcille catchment confirmed that vegetative filter strips can effectively reduce diuron fluxes in surface runoff (>80% abatement) and infiltration water (>70% abatement). The full dataset offers a valuable resource for the validation of hydrological models and the development of global approaches to better understand the pressure–transport–exposure–impact chain and aquatic community resilience at the small catchment scale. [ABSTRACT FROM AUTHOR]

A buffer zone is a belt of shelter or permanent grassland separating agricultural land from watercourses and water reservoirs. According to the Code of Good Agricultural Practices, they are a landscape element that can limit the migration of biogenic substances. Increasing attention is paid to the fact that these barriers are effective during the growing season. However, in the autumn-winter and early-spring half-year they can be a source of nitrogen compounds leached from the catchment to surface water. In connection with this, research was undertaken to assess the content of nitrogen compounds in the soil of the zone at the channel and water of the watercourse in a small agricultural catchment. The processes occurring in the buffer zones leading to the release of biogenic compounds do not only concern leaching them to surface and groundwater, therefore the amount of nitrous oxide emissions, which is the result of the denitrification process occurring in the soil, was examined. Based on the obtained results, it was found that an increased content of nitrogen compounds in the soil of buffer zones may have an impact on the increased emission of N2O and an increased content of these substances in surface water.

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.

Gowienica Miedwiańska river, located in a typical agricultural catchment, was selected for the research. They were carried out in 2014-2015. Samples of bottom sediments from the river were collected from the 0-30 cm layer. In the samples taken, the total content of the elements was determined: Ca, Cu, Fe, K, Mg, Mn, Na, Zn. The aim of the research was to initially monitor the spread of macro- and microelements in bottom sediments of the Gowienica River along its course. The analyzes performed in the bottom sediment samples allowed to observe that the highest concentrations of the analyzed elements in both 2014 and 2015 occurred in the final section of the studied river (P-5 and 6) with the exception of zinc concentrations, where the highest concentration occurred in the initial section in point no. 2. Increased concentrations may be caused by a slowing down of the river water speed. The highest statistically significant positive correlations for the deposits of the Gowienica River appeared between magnesium and sodium in 2014 and 2015. The analysis also showed statistically significant correlations for calcium and copper (in 2014 and 2015) and for calcium and manganese in 2014 and 2015.

In several countries around the world, agricultural land area exceeds 70% (Uruguay 82.6%, Kazakhstan 80.4%, Turkmenistan 72.0%, Great Britain 71.7%, Ukraine 71.6% and others). This poses a serious risk of dissipating nitrates into the aquatic environment in agricultural catchments. The aim of this study was to assess the impact of land use on water quality parameters in an agricultural catchment area. It was decided to select for analysis the catchment of the Orla River (river length of 88 km, catchment area of 1,546 km2). The catchment area is predominantly agricultural in character and its entire area has been declared as an agricultural nitrate vulnerable zone (NVZ). A total of 27 survey sites were selected on the main watercourse and its tributaries. Analyses were conducted in the years 2010–2012 to determine physical and chemical parameters of water (pH reaction, conductivity, dissolved oxygen, total nitrogen, organic nitrogen, ammonia nitrogen, nitrates, total and reactive phosphorus) as well as six macrophyte metrics of ecological status assessment (MIR, IBMR, RMNI, MTR, TIM, RI). The average values of most physico-chemical parameters of water quality repeatedly exceeded limits of good ecological status, both in the Orla River and its tributaries. As many as 18 survey sites were classified as moderate ecological status, five sites as poor and only four as good ecological status. The results indicate the impact of land use in the catchment on water conductivity. Differences were observed in the concentrations of biotic components in the main watercourse and its tributaries, and in water quality in the southern part of the catchment in relation to the rest of the study area. This is probably connected with a greater share of forests and surface waters in that area.

Forty-eight suspended particulate matter (SPM) samples were collected from the Mun River, northeast Thailand and its junction with the Mekong River, to investigate the relationship between the distribution of rare earth elements (REE) in SPM and the soils in the watershed. The total REE contents (∑REE) in SPM in the Mun River ranged from 78.5 to 377.8 mg/kg with the average of 189.3 mg/kg, which was lower than ∑REE of 222.3 mg/kg at the Mekong River (one sample at junction). The Post Archean Australia Shale (PAAS)-normalized ratios of light REE (LREE), middle REE (MREE) and heavy REE (HREE) were averaged to 1.0, 1.3 and 1.0, which showed a clear enrichment in MREE. In short, along the Mun River, the REE contents in SPM were decreasing, and the PAAS-normalized patterns of REE showed gradually flat. The REE content in SPM and soils are highest in the upper catchment, indicating that soil/bedrock is the most important source of REE in SPM. Additionally, the positive Eu anomaly was enhanced by the higher Ca content in SPM (R = 0.45), which may be caused by more feldspars or carbonates with Ca and Eu substituting Ca. The results present the REE behaviors of SPM in the Mun River and relationship between REE in SPM and soil/bedrock, the findings may support the other studies in catchment weathering.

We introduce the freely available web‐based Water in an Agricultural Landscape—NUčice Database (WALNUD) dataset that includes both hydrological and meteorological records at the Nučice experimental catchment (0.53 km2), which is representative of an intensively farmed landscape in the Czech Republic. The Nučice experimental catchment was established in 2011 for the observation of rainfall–runoff processes, soil erosion processes, and water balance of a cultivated landscape. The average altitude is 401 m a.s.l., the mean land slope is 3.9%, and the climate is humid continental (mean annual temperature 7.9°C, annual precipitation 630 mm). The catchment is drained by an artificially straightened stream and consists of three fields covering over 95% of the area which are managed by two different farmers. The typical crops are winter wheat, rapeseed, and alfalfa. The installed equipment includes a standard meteorological station, several rain gauges distributed across the basin, and a flume with an H‐type facing that is used to monitor stream discharge, water turbidity, and basic water quality indicators. Additionally, the groundwater level and soil water content at various depths near the stream are recorded. Recently, large‐scale soil moisture monitoring efforts have been introduced with the installation of two cosmic‐ray neutron sensors for soil moisture monitoring. The datasets consist of observed variables (e.g. measured precipitation, air temperature, stream discharge, and soil moisture) and are available online for public use. The cross‐seasonal, open access datasets at this small‐scale agricultural catchment will benefit not only hydrologists but also local farmers. [ABSTRACT FROM AUTHOR]

In several countries around the world, agricultural land area exceeds 70% (Uruguay 82.6%, Kazakhstan 80.4%, Turkmenistan 72.0%, Great Britain 71.7%, Ukraine 71.6% and others). This poses a serious risk of dissipating nitrates into the aquatic environment in agricultural catchments. The aim of this study was to assess the impact of land use on water quality parameters in an agricultural catchment area. It was decided to select for analysis the catchment of the Orla River (river length of 88 km, catchment area of 1,546 km2). The catchment area is predominantly agricultural in character and its entire area has been declared as an agricultural nitrate vulnerable zone (NVZ). A total of 27 survey sites were selected on the main watercourse and its tributaries. Analyses were conducted in the years 2010-2012 to determine physical and chemical parameters of water (pH reaction, conductivity, dissolved oxygen, total nitrogen, organic nitrogen, ammonia nitrogen, nitrates, total and reactive phosphorus) as well as six macrophyte metrics of ecological status assessment (MIR, IBMR, RMNI, MTR, TIM, RI). The average values of most physico-chemical parameters of water quality repeatedly exceeded limits of good ecological status, both in the Orla River and its tributaries. As many as 18 survey sites were classified as moderate ecological status, five sites as poor and only four as good ecological status. The results indicate the impact of land use in the catchment on water conductivity. Differences were observed in the concentrations of biotic components in the main watercourse and its tributaries, and in water quality in the southern part of the catchment in relation to the rest of the study area. This is probably connected with a greater share of forests and surface waters in that area. [ABSTRACT FROM AUTHOR]

Diffuse sources of pollution like agricultural or urban runoff are important factors in determining the quality of surface waters, although they are more difficult to monitor than point sources. The objective of our study was to verify assumptions that the inflow from agricultural nutrient sources is higher than from urbanized ones. It has been done by comparing the nutrients and organic matter concentrations and loads for three small streams in northern Poland (Pomerania Region). Two streams flowing through agricultural catchments and an urban stream flowing through the city of Gdansk were analysed. Concentrations of nutrients: N-NO ${}_{3}^{-}$ 3 − N-NH ${}_{4}^{+}$ 4 + , P-PO ${}_{4}^{3-}$ 4 3 − , total phosphorus, total nitrogen and COD were measured 1–3 times per month in the period from July 2017 to December 2018 in agricultural watersheds and from October 2016 to March 2018 for an urban stream. Seasonal changes in concentrations were analysed with descriptive statistics tools. Principal Component Analysis (PCA) was used to point out the most significant factors determining variations in nutrients and organic matter concentrations with respect to different seasons. The factors included a number of characteristics regarding the catchment and streams: total catchment area, stream length, watershed form ratio, stream slope, flow rate and land use with respect to paved areas, agricultural areas and green areas (parks, forests, meadows and pastures). Although concentrations of nitrogen compounds were higher in streams flowing through agricultural areas, our study showed that total concentrations of phosphorus were higher in the urban stream, especially in summer. In agricultural areas the summer concentrations of nutrients were not high, which was probably due to dense vegetation. The correlation between P-PO ${}_{4}^{3-}$ 4 3 − concentration and size of agricultural area in the catchment was observed in winter when no vegetation field cover exists. Our study shows an urgent need to monitor the nutrient loads carried with urban streams especially if discharged into receivers prone to eutrophication.

Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy–Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter–spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions. [ABSTRACT FROM AUTHOR]

Tracer studies have been key to unravelling catchment hydrological processes, yet most insights have been gained in environments with relatively low human impact. We investigated the spatial variability of stream isotopes and water ages to infer dominant flow paths in a ~10‐km2 nested catchment in a disturbed, predominantly agricultural environment in Scotland. We collected long‐term (>5 years) stable isotope data of precipitation, artificial drainage, and four streams with varying soil and land use types in their catchment areas. Using a gamma model, Mean Transit Times (MTTs) were then estimated in order to understand the spatial variability of controls on water ages. Despite contrasting catchment characteristics, we found that MTTs in the streams were generally very similar and short (<1 year). MTTs of water in artificial drains were even shorter, ranging between 1 to 10 months for a typical field drain and <0.5 to 1 month for a country road drain. At the catchment scale, lack of heterogeneity in the response could be explained by the extensive artificial surface and subsurface drainage, "short‐circuiting" younger water to the streams during storms. Under such conditions, additional intense disturbance associated with highway construction during the study period had no major effect on the stream isotope dynamics. Supplementary short‐term (~14 months) sampling of mobile soil water in dominant soil‐land use units also revealed that agricultural practices (ploughing of poorly draining soils and soil compaction due to grazing on freely draining soils) resulted in subtle MTT variations in soil water in the upper profile. Overall, the isotope dynamics and inferred MTTs suggest that the evolution of stream water ages in such a complex human‐influenced environment are largely related to near‐surface soil processes and the dominant soil management practices. This has direct implications for understanding and managing flood risk and contaminant transport in such environments. [ABSTRACT FROM AUTHOR]

Diffuse sources of pollution like agricultural or urban runoff are important factors in determining the quality of surface waters, although they are more difficult to monitor than point sources. The objective of our study was to verify assumptions that the inflow from agricultural nutrient sources is higher than from urbanized ones. It has been done by comparing the nutrients and organic matter concentrations and loads for three small streams in northern Poland (Pomerania Region). Two streams flowing through agricultural catchments and an urban stream flowing through the city of Gdansk were analysed. Concentrations of nutrients: N-NO-3 N-NHC+ 4, P-PO3- 4, total phosphorus, total nitrogen and COD were measured 1-3 times per month in the period from July 2017 to December 2018 in agricultural watersheds and from October 2016 to March 2018 for an urban stream. Seasonal changes in concentrations were analysed with descriptive statistics tools. Principal Component Analysis (PCA) was used to point out the most significant factors determining variations in nutrients and organic matter concentrations with respect to different seasons. The factors included a number of characteristics regarding the catchment and streams: total catchment area, stream length, watershed form ratio, stream slope, flow rate and land use with respect to paved areas, agricultural areas and green areas (parks, forests, meadows and pastures). Although concentrations of nitrogen compounds were higher in streams flowing through agricultural areas, our study showed that total concentrations of phosphorus were higher in the urban stream, especially in summer. In agricultural areas the summer concentrations of nutrients were not high, which was probably due to dense vegetation. The correlation between P-PO3- 4 concentration and size of agricultural area in the catchment was observed in winter when no vegetation field cover exists. Our study shows an urgent need to monitor the nutrient loads carried with urban streams especially if discharged into receivers prone to eutrophication. [ABSTRACT FROM AUTHOR]

Anthropogenic activities alter the underlying surface conditions and arrangements of landscape features in a drainage basin, interfering with the pollutant (e.g., dissolved nitrogen, phosphorus) transport network configuration and altering the hydrological response. Assessing the impact of anthropogenic activities on hydrological connectivity for natural-artificial catchment is critical to understand the hydrological-driven ecosystem processes, services and biodiversity. However, quantifying this impact at catchment scale remains challenging. In this study, a new framework was proposed to quantify the impact of anthropogenic activities on hydrological connectivity combined with graph theory and network analysis. This framework was exemplified in a natural-artificial catchment of the Yangtze River basin of China. Based on remote sensing and field-investigated data, three transport networks were constructed, including natural transport network (N1), ditch–road transport network (N2), and terrace–dominated transport network (N3), which reflected the different human intervention. The results showed that human intervention improved the connectivity of the nodes and enhanced the complexity of the catchment transport network structure. Anthropogenic activities significantly decreased the hydrological structural connectivity of the catchment. In particular, compared with the N1 network, the critical nodes for hydrological connectivity which were judged by connectivity indexes were reduced by 92.94% and 95.29% in the N2 and N3 network, respectively. Furthermore, the ditch–road construction had a greater impact than terraces in decreasing hydrological structural connectivity at catchment scale. This framework has proven effective in quantifying the hydrological connectivity analysis under different human intervention at the catchment scale and facilitates the improvement of catchment management strategies. • A new framework was proposed to identify catchment hydrological connectivity. • Graph theory combined with network analysis were integrated into the framework. • Three transport networks were constructed to exemplify the framework. • Ditches, roads, and terraces significantly decreased hydrological connectivity. [ABSTRACT FROM AUTHOR]

The quality of surface water is shaped by a number of processes taking place across the catchment. The dominant role in shaping changes in physico-chemical properties of water play hydrochemical conditions. Detailed characteristics of the aquatic environment is an important aspect in assessing the variability of temporary surface water quality, and the information is necessary for sustainable water management. Therefore, the aim of this study was to investigate the seasonal variability of the chemical composition of water of a small stream in the agricultural landscape in north-eastern Poland. The study included analysis of selected physico-chemical properties of water per year, performing factor analysis in order to identify the processes that shape seasonal changes and the calculation of indicators Markham (index of seasonality and time of concentration). The results found that the physico-chemical properties of water examined watercourse been subject seasonal fluctuations. It indicates the relationship between the content of the individual components dissolved and the size of flow. It was found that in conditions of Polish north-eastern intensive washing and increased levels of nutrients were observed during high water caused by melting snow and rainfall in winter and early spring. Therefore, this period can be critical for the quality of surface water in the agricultural landscape.

Ponds in agricultural areas are ubiquitous water retention systems acting as reactive biogeochemical hotspots controlling pesticide dissipation and transfer at the catchment scale. Several issues need to be addressed in order to understand, follow-up and predict the role of ponds in limiting pesticide transfer at the catchment scale. In this review, we present a critical overview of functional processes underpinning pesticide dissipation in ponds. We highlight the need to distinguish degradative and non-degradative processes and to understand the role of the sediment-water interface in pesticide dissipation. Yet it is not well-established how pesticide dissipation in ponds governs the pesticide transfer at the catchment scale under varying hydro-climatic conditions and agricultural operation practices. To illustrate the multi-scale and dynamic aspects of this issue, we sketch a modelling framework integrating the role of ponds at the catchment scale. Such an integrated framework can improve the spatial prediction of pesticide transfer and risk assessment across the catchment-ponds-river continuum to facilitate management rules and operations.

A lot of attention has been given to the importance of riparian zones as a nitrogen buffer during the last 30 years. Expectations were high and have resulted often in mismanagement practices. This paper aims at revisiting during this period the main research advancement, questions generated, and the progress in understanding the role of interactions between land and water in river system functioning. We describe how the seminal papers published in the 1980s on the role of riparian zone as nitrogen buffer have triggered several fundamental and applied questions related to the mechanisms at stake or their long efficiency in different hydrological and climatic contexts. We then address how this local riparian buffer capacity can be evaluated at the small drainage basin scale. We finally touch upon the restoration and protection of riparian zones in the context of climate change and especially its potential role on local and global water fluxes and other key aquatic ecosystem functions. [ABSTRACT FROM AUTHOR]

Pesticide transfers and fate are highly influenced by the presence of discontinuities such as grass strips, slopes, hedgerows or roads that can accelerate or slow down and dissipate water and contaminant fluxes. That is why those landscape elements must be integrated into watershed management plans. It implies taking them into account when modeling water and contaminant fluxes at the small catchment scale. However, if the influence of landscape elements has already been widely explored at field scale, models generally do not reach the catchment scale. The project PESHMELBA aims at developing a new modeling tool of water and contaminants circulation and fate at the scale of small catchments in order to optimize landscape organization. The model explicitly takes into account spatial organization of landscape by representing existing elements, their locations and shapes. The final aim of this modeling tool is to efficiently test and rank different development scenarios in order to assess the influence of agricultural practices, land uses and landscape management strategies on water quality. In PESHMELBA, dominating processes ruling water and contaminants circulation and dissipation for each element type are mainly represented by existing and validated models. New components have also been developed when no suitable model was found in the literature. All these models present different levels of conceptualization and are used as modeling units ensuring a modular structure. Then, the different units are gathered and connected in the OpenPALM coupler (Fouilloux and Piacentini, 1999) in order to implement the spatial and temporal couplings. This innovative approach leads to a spatialized model of the whole catchment. Applications cases are tested with an increasing complexity, from a case with two plots to the hillslope scale with several plots, ditches and rivers. They show that PESHMELBA is a promising tool to compare scenarios considering water and pesticide fate in different complex landscapes. Unlabelled Image • PESHMELBA model simulates dynamic behavior of pesticide in agricultural catchments. • Modules, each representing an element of the landscape, are coupled in space and time. • PESHMELBA allows for easy inclusion of new components and processes. • The tool is suited to optimize management scenarios for decision-making issues. • Applications on contrasted hillslope configurations show the potential of the tool. [ABSTRACT FROM AUTHOR]

Highlights • Field P balances increased over the study period in two mixed land use catchments. • Soil P changes were inconsistent, increasing and decreasing between catchments. • There is scope for better distribution of P sources, particularly organic manures. • Knowledge transfer needs to support better nutrient management planning on farms. Abstract Reducing legacy soil phosphorus (P) is recognised as an effective measure to mitigate diffuse P losses from agricultural landscapes and alleviate trophic pressure to freshwaters systems. Accounting for the distribution of P within farms is critical in identifying fields of agronomic underperformance and/or environmental risk to water as a consequence of inadequately managed re-cycling of P. There is also a need to understand how P use and legacy soil P evolves under the Nitrates Action Programme (NAP) regulations from the European Union (EU) Nitrates Directive. In an Irish case study the aim was to provide a systematic and detailed audit of P balance and soil P responses and trends in two mixed land use agricultural catchments (Arable A and B) across a four year study period. Driven by increased mineral P inputs the field balances in the Arable A catchment had an average surplus P, ranging from 1.9 to 7.5 kg ha−1 yr−1. However, between the study period 2010 to 2013, the average soil test P (STP) levels declined, with the area of excessive soil P concentrations decreasing by 8%. Similarly, in the Arable B catchment the average annual P inputs increased the surplus field P from -0.42 to 25.5 kg ha−1 yr−1, but the area of excessive soil P concentrations increased by 4%. In part, this increase is attributed to some fields receiving excess applications of organic nutrient forms above crop requirements. Whilst, the legacy soil P declined in the Arable A catchment indicating a response to NAP, for both catchments it is evident that the distribution of P sources within farms was poor and P inputs often did not match crop and soil P requirements at the field scale. This study highlights the need for improved support to knowledge transfer mechanisms that can deliver better farm and soil specific nutrient management planning strategies. Without this consideration, achieving the dual benefits of improvement to water quality and increased crop output from agricultural landscapes will be restricted. [ABSTRACT FROM AUTHOR]

A buffer zone is a belt of shelter or permanent grassland separating the agricultural land from watercourses and water reservoirs. According to the Code of Good Agricultural Practices, they constitute a landscape element that can limit the migration of biogenic substances. Increasing attention is paid to the fact that these barriers are effective during the growing season. However, in the autumn-winter and early-spring half-year, they can be a source of nitrogen compounds leached from the catchment to the surface water. In connection with this, research was undertaken to assess the content of nitrogen compounds in the soil of the zone at the channel and water of the watercourse in a small agricultural catchment. The processes occurring in the buffer zones leading to the release of biogenic compounds do not only concern leaching them to surface and groundwater; therefore, the amount of nitrous oxide emissions, which is the result of the denitrification process occurring in the soil, was examined. On the basis of the obtained results, it was found that an increased content of nitrogen compounds in the soil of buffer zones may have an impact on the elevated emission of N2O and a raised content of these substances in surface water. [ABSTRACT FROM AUTHOR]

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Currently, pesticides are massively used in agricultural areas end up in watercourses, as they are usually final receptacles of organic contamination. A large number of wetlands such as ponds occurred in agricultural catchments. They are dynamic and complex systems which contains different compartments like the water column, sediments and biota. The sediment compartment can store contaminants according to their physicochemical properties, but this process is continuously challenged because of settling and resuspension mechanisms. The role of the sediments regarding pesticides behavior and their fate is still poorly investigated. Our study aimed to fill this gap, particularly considering the Bassioué pond, which is located in the carbonated agricultural upper sub-catchment of the Auradé critical zone observatory (Gers, France), with a wheat/sunflower crop rotation and a steep slope enhancing erosion phenomenon. We focused on pesticide storage in the sediments which represent the main compartment due to the environmental conditions. Our current objective was to understand (i) how and where pesticides are stored in the sediments, and (ii) the relationship with the characteristics of sediments, supposed to be highly involved in the storage and degradation of pesticides. Two field campaigns were carried out to collect sediment samples within a regular quadrat from the inlet to the outlet of the pond in autumn 2019 and summer 2020 at different depth. A set of three pesticide was quantified as well as sediment texture. The results highlighted that sediment particle size distribution varied between upstream and downstream of the pond: from the finest to the coarsest; as did the spatial distribution of pesticides. This reveled that pesticides were partly controlled by their physicochemical properties: most hydrophilic pesticides had greater affinity with the finest fractions of the sediments. A difference in pesticide storage according to the depth has been observed, especially for boscalid (logKOW = 3) which was found in greater quantities in the deepest samples, with increasing coarse silt content. Finally, a seasonal effect was also observed on pesticide levels, as their presence was highly driven by firstly their uses in the catchment and secondly by the soil erosion occurring during intense spring flood events. This work provides new knowledge on the role of ponds in pesticide storage, dissipation and transfer downstream, which can·be used for agricultural landscape management.

Microplastics have received widespread attention as an emerging pollutant in recent years, but limited studies have explored their response to extreme weather. This study surveyed and analyzed the occurrence and distribution of microplastics in a typical agricultural catchment located on the Loess Plateau, focusing on their response to heavy rainstorms. Microplastics were detected in all soil samples with an abundance of 70–4020 items/kg, and particles less than 0.5 mm accounted for 81.61 % of the total microplastics. The main colors of microplastic were white, yellow, and transparent, accounting for 38.50 %, 32.90 %, and 21.05 % respectively, and the main shapes were film and fragment, accounting for 47.65 % and 30.81 %. Low density polyethylene was the main component of microplastics identified using Fourier transform infrared spectrometry. The extensive use of plastic mulch film is a major contributor to microplastic pollution in this catchment. The differences and connections observed in microplastics imply mutual migration and deposition within the catchment. A check dam at the outlet effectively intercepts microplastics during the rainstorm, reducing the microplastic by at least 6.1 × 1010 items downstream. This study provides a reference for the effects of rainstorms on the sources and pathways of MP pollution in regions prone to severe soil erosion. [Display omitted] • Fragmentation of plastic mulch film is a primary source of MPs in farmland. • Extreme rainstorm enhances the migration of MPs in agricultural catchment. • MPs can migrate and transform among different land types within the catchment. • Check dam can intercept significant amount of MPs to reach downstream area. [ABSTRACT FROM AUTHOR]

• Runoff NO 3 −-N loss dominated by soil n mineralization. • Rapeseed cake exacerbated runoff NO 3 −-N loss by increased soil n mineralization. • Green manure reduced the soil n mineralization compared to rapeseed cake. • Green manure mulching was the effective measure to reduce runoff NO 3 −-N loss. Nitrate-nitrogen (NO 3 −-N) loss is a significant contributor to water quality degradation in agricultural catchments. The amount of nitrogen (N) fertilizer input in citrus orchard is relatively large and results in significant NO 3 −-N loss, compared to cropland. To promote sustainable N fertilizer management, it is crucial to identify the sources of runoff NO 3 −-N loss in citrus orchards catchments. Particularly, we poorly know the sources of NO 3 −-N and the mitigation mechanisms in these areas, which are highly polluted with NO 3 −-N in water bodies. In this study conducted in central China, we conducted a field experiment with four treatments (CK: no N fertilizer; CF: conventional N fertilizer, 371.3kg N ha−1 yr−1 urea; OM: CF with organic manure; GM: CF with legume green manure) and a catchment-scale experiment in two citrus orchards (34.3%; 51.6%) catchments. To determine the source of runoff NO 3 −-N loss, we used the dual isotope tracer method (δ15N and δ18O of NO 3 −) to identify the sources of NO 3 −-N, and a 15-day incubation experiment to determine the potential and rate of soil N mineralization. Our findings revealed that soil organic nitrogen (SON) mineralization was the primary contributor to runoff NO 3 −-N loss, and soil N mineralization potential (0.65⁎⁎⁎) and rate (0.54⁎⁎⁎) were the key factors impacting NO 3 −-N loss. Interestingly, organic manure significantly increased 29.0% of NO 3 −-N loss derived from SON in the runoff by enhancing soil N mineralization potential (+36.6%) and rate (+77.1%). But green manure mulching significantly reduced the soil N mineralization rate (-18.6%) compared to organic manure application, making it the most effective measure to reduce NO 3 −-N loss (-12.4%). Our study highlights the critical role of regulating SON mineralization in controlling NO 3 −-N pollution in surface waters in citrus orchard catchments. [Display omitted] [ABSTRACT FROM AUTHOR]

The growing water deficit and the increased demand for water, as well as economic problems and inadequate spatial planning in many regions indicate a necessity of developing more effective rules of programming and realisation of works concerning the water management in small catchments. The paper presents a sample analysis of the possibilities of increasing water retention in the agricultural loess catchments with periodic streams. The scope of the study included the determination of physical parameters of selected sub-catchments (geometry, soil cover, land use, etc.) and of the sources of threat to water resources, resulting from construction and geomorphological conditions. Pre-design assumptions of dammings were developed, taking into account anti-erosion protective measures, and treatments increasing the landscape retention of water were proposed. Creating surface retention objects should be an important source of water in simplified agroecosystems, especially in regions, where productivity to a great extent depends on natural weather conditions. Proper management of the fourth-order loess basin of the Ciemięga River (area of about 150 km2, the presence of 50 lateral valleys) could give a temporary reservoir retention reaching 500 thousand m3. Farmers should be encouraged to seek “own water sources” (including the accumulation of water within wasteland), using appropriate economic instruments (tax reliefs for the documented volume of retained water, e.g. in small retention reservoirs).

Studies on the influence of hydrological and meteorological events to leaching of NO3-, NH4+ and PO43- were carried out in the years 2009 and 2010, in a small agricultural catchment near Bialystok. The results of measurements of weather conditions, rate of flow and chemical composition of the flow were presented in the work. It was found that a sudden rainfall is a critical period for courses in the agricultural landscape. The concentration of dissolved substances increases during the increased flow of water in the watercourse, whereas it decreases during the low water levels. In the year 2009, during the summer of a small stream of water transported about 365 kg load of nitrate, 12 kg of ammonium ions and about 5 kg of phosphate. However, in the year 2010 in the months of May – September, approximately 1139 kg load of nitrate, 8 kg of ammonium ions and about 19 kg of phosphate. Therefore, the flooding caused by pouring rains is a period of intense leaching of NO3-, NH4+ and PO43-.

In recent years, research was carried out on pathways of substances dissolved in the agricultural catchments. The proportions in which the total outflow involves the forms of water migration: runoff, subsurface and baseflow are important for translocation of pollutants are. The study showed that the share of individual migration routes in the basin is variable in space and time in agricultural catchment. In the North-Eastern Poland the most intense period of chemical denudation is snowmelt. Therefore, early spring melt is critical for water quality . In addition, part of the outflow of highly contaminated are tile drain outflow in agricultural catchments.

Despite global efforts to monitor water quality in catchments worldwide, tropical and subtropical zones still lack data to study the influence of human activities and climate variations on solute dynamics. In this study, we monitored ten solutes every two weeks for six years (2010–2015) in three nested catchments (2 to30 km 2 ), which contained heterogeneous landscapes composed of forests and agricultural land, and one small neighboring forested catchment (0.4 km 2 ). Data analysis revealed that i) rainfall, discharge and solute concentrations displayed no clear seasonal patterns, unlike many catchments of the temperate zone; ii) solute concentrations in the agricultural area were higher than those in the forested area, but both areas displayed similar temporal patterns due to a common hydroclimatic driver; iii) all four catchments displayed a chemostatic export regime for most of the solutes, similar to catchments of the temperate zone; and iv) a positive correlation was observed between anion concentrations and ENSO (El Niño-Southern Oscillation) index. ENSO appeared to influence both hydroclimatic and anion dynamics in these subtropical catchments. [ABSTRACT FROM AUTHOR]

A large part of the organic carbon in streams is transported by pulses of terrestrial dissolved organic carbon (tDOC) during hydrological events, which is more pronounced in agricultural catchments due to their hydrological flashiness. The majority of the literature considers stationary benthic biofilms and hyporheic biofilms to dominate uptake and processing of tDOC. Here, we argue for expanding this viewpoint to planktonic bacteria, which are transported downstream together with tDOC pulses, and thus perceive them as a less variable resource relative to stationary benthic bacteria. We show that pulse DOC can contribute significantly to the annual DOC export of streams and that planktonic bacteria take up considerable labile tDOC from such pulses in a short time frame, with the DOC uptake being as high as that of benthic biofilm bacteria. Furthermore, we show that planktonic bacteria efficiently take up labile tDOC which strongly increases planktonic bacterial production and abundance. We found that the response of planktonic bacteria to tDOC pulses was stronger in smaller streams than in larger streams, which may be related to bacterial metacommunity dynamics. Furthermore, the response of planktonic bacterial abundance was influenced by soluble reactive phosphorus concentration, pointing to phosphorus limitation. Our data suggest that planktonic bacteria can efficiently utilize tDOC pulses and likely determine tDOC fate during downstream transport, influencing aquatic food webs and related biochemical cycles. [ABSTRACT FROM AUTHOR]

Abstract: The change in land use and land cover (LULC) from natural vegetation to agricultural in mountain areas usually dramatically accelerates soil erosion rates if the land is used for crop production. The aim of research was to calculate soil erosion magnitude basing on the Revised Universal Soil Loss Equation (RUSLE) in response to long‐term changes in LULC in an agricultural Homerka catchment (19.3 km2) of the Polish Carpathians. The changes in LULC were derived from cadastral maps for 1846 and orthophotomaps for 2009. Three variants with different factors, rainfall–run‐off erosivity (R), practice support (P), and LULC, were analysed to investigate which has had the greatest impact on soil erosion changes over the last 160 years. An increase in forest area (by 67.81%) and decrease in cultivated land (by 91.94%) were observed, primarily due to the collapse of the communist system. The estimated soil erosion using the RUSLE model in the analysed catchment decreased by 77% (from 18.13 t ha−1 yr−1 in 1846 to 4.11 t ha−1 yr−1 in 2009). The long‐term changes in soil erosion rates and their spatial distribution are mainly associated with transformation from cultivated land to forest or grassland. The P factor was responsible for reduction of soil erosion rates by 8%, a minor impact. Over the last 160 years, the average and maximum annual precipitation changes were also statistically insignificant. Results reveal a dominant role of human impact, particularly with respect to LULC on soil erosion changes in mid‐mountain areas. [ABSTRACT FROM AUTHOR]

We investigated temporal variations and vertical evolution of dissolved gaseous tracers (CFC-11, CFC-12, SF 6 , and noble gases), as well as 3 H/ 3 He ratio to determine groundwater recharge processes of a shallow unconfined, hard-rock aquifer in an agricultural catchment. We sampled dissolved gas concentration at 4 locations along the hillslope of a small experimental watershed, over 6 hydrological years, between 2 and 6 times per years, for a total of 20 field campaigns. We collected groundwater samples in the fluctuation zone and the permanently saturated zone using piezometers from 5 to 20 m deep. The purpose of this work is i ) to assess the benefits of using gaseous tracers like CFCs and SF6 to study very young groundwater with flows suspected to be heterogeneous and variable in time, ii ) to characterize the processes that control dissolved gas concentrations in groundwater during the recharge of the aquifer, and iii ) to understand the evolution of recharge flow processes by repeated measurement campaigns, taking advantage of a long monitoring in a site devoted to recharge processes investigation. Gas tracer profiles are compared at different location of the catchment and for different hydrologic conditions. In addition, we compare results from CFCs and 3 H/ 3 He analysis to define the flow model that best explains tracer concentrations. Then we discuss the influence of recharge events on tracer concentrations and residence time and propose a temporal evolution of residence times for the unsaturated zone and the permanently saturated zone. These results are used to gain a better understanding of the conceptual model of the catchment and flow processes especially during recharge events. [ABSTRACT FROM AUTHOR]

Knowledge of the dominant water sources and their relative contributions to streams in time is important for understanding the underlying hydrological processes as well as managing the quantity and quality of water resources. In many subtropical regions, the complexity of mixed agricultural land and water use in combination with lack of data further inhibits such understanding of the dominant catchment scale runoff generation processes. This study provides new insights into the time-variable interactions of natural and anthropogenic influences on the catchment response through integrated hydrometric and multi-tracer (stable water isotopes, Mg 2+ , Na + , Si 4+ , Cl − , and Electricity Conductivity) analyses. The combined diagnostic tools of mixing models (DTMM) and end-member mixing analysis (EMMA) were successfully used to evaluate the spatiotemporal variability in key water sources of a subtropical catchment in China. This study site is characterized by rain-fed uplands and irrigated water paddy fields. The EMMA results for one year of data showed that irrigation water, rainwater and ground water were the three main sources, which contributed to 64%, 19% and 17% of the streamflow on average, respectively. However, temporal patterns in rainfall and irrigation practices did cause significant variability in these relative contributions. Overall, we found that routine agricultural practices to optimize crop growth (especially during paddy growth periods) was a more important factor than hydro-meteorological conditions in controlling the regime and properties of water sources. The relatively simple but successful application of EMMA and DTMM in a complex environment demonstrates that it is a valuable approach for understanding water sources and hydrologic processes concerning agricultural or mixed-land use catchments. [ABSTRACT FROM AUTHOR]

Waterborne microbial pollution remains poorly understood in developing countries, especially in rural areas. The transport of point (e.g. untreated domestic wastewater) and non-point sources of fecal bacteria such as Total coliform (TC) and Escherichia coli ( E. coli ) and their spatial and temporal patterns were identified in a typical small agricultural catchment in a hilly area of subtropical China. Over the sampling area, 460 water samples from 24 sites were collected during a period of 12 months, and a remediation option using an existing ecological ditch was evaluated. The results showed that 70% surface water samples exceeded the guideline of 1000 TC MPN 100 ml −1 in the catchment. Also, 90% of groundwater samples exceeded the guideline of 10 MPN E. coli 100 ml −1 for safe drinking water. Higher concentrations of TC and E. coli occurred both in the warm and rainy season in surface water and groundwater. TC and E. coli concentrations in surface water tributaries and groundwater near residential areas were greater than those in downstream water bodies. A 300 m long vegetated ecological ditch greatly reduced average concentrations TC of 97.7% and E.coli of 99.5%. TC and E. coli concentrations were significantly correlated with electrical conductivity and turbidity, both in surface water and groundwater, indicating that mixtures of organic colloids and sediment were the most important transport vector for pathogens. However, temperature only showed a controlling effect on bacteria concentration in groundwater in this particular catchment. The current research could help predict microbial risks and establish integrated management strategy to improve water quality in the hilly agricultural catchments in the subtropical region. [ABSTRACT FROM AUTHOR]