Water Quality In Agricultural Catchments Research Articles

Mapping the potential for Payments for Ecosystem Services schemes to improve water quality in agricultural catchments: A multi-criteria approach based on the supply and demand concept

Payments for Ecosystem Services (PES) schemes are an increasingly popular form of catchment management for improving surface water and groundwater quality. In these schemes, downstream water users who are impacted by agricultural diffuse pollution incentivise upstream farmers to adopt better practices. However, this type of scheme will not be successful in all situations, in part, due to a lack of potential for agriculture to improve the suuply of good water quality and/or a lack in demand from downstream users for good water quality. As such, this study aims to present a flexible approach to mapping the potential for PES schemes to improve water quality in agricultural catchments. The approach is based on multi-criteria analysis, with supply and demand as key criteria. It uses expert judgement or current guidance on PES to select supply and demand sub-criteria, expert judgement to weight all criteria through pairwise comparisons and readily available, national datasets to indicate criteria. Once indicator data are normalized, it combines them in a weighted sums analysis and presents results spatially at the national scale, all within a geographical information system. The approach can easily be applied to the country or region of interest by using locally relevant criteria, expert judgement and data. For example, when applied to the situation for river waterbodies in England, supply sub-criteria were the contribution of agriculture to loads of the major pollutants (nitrogen, phosphorus and sediments) and demand sub-criteria were the different downstream water users present (water companies and, tourist and local recreational users). Experts assigned equal weight to supply and demand criteria and the highest weights to sediments and water companies for sub-criteria, respectively. When national scale datasets to indicate these criteria were combined in a weighted sums analysis, it was possible to identify areas of high potential for PES. This would hopefully motivate more detailed research at the individual catchment level into the constraints in linking supply and demand. Three case-study schemes were also examined to show how some of these constraints are being identified and overcome. As such, the approach forms the first tier in a two-tier framework for establishing PES schemes to improve water quality in agricultural catchments.

Climate effects on land management and stream nitrogen concentrations in small agricultural catchments in Norway

Land use and climate change can impact water quality in agricultural catchments. The objectives were to assess long-term monitoring data to quantify changes to the thermal growing season length, investigate farmer adaptations to this and examine these and other factors in relation to total nitrogen and nitrate water concentrations. Data (1991–2017) from seven small Norwegian agricultural catchments were analysed using Mann–Kendall Trend Tests, Pearson correlation and a linear mixed model. The growing season length increased significantly in four of seven catchments. In catchments with cereal production, the increased growing season length corresponded to a reduction in nitrogen concentrations, but there was no such relationship in grassland catchments. In one cereal catchment, a significant correlation was found between the start of sowing and start of the thermal growing season. Understanding the role of the growing season and other factors can provide additional insight into processes and land use choices taking place in agricultural catchments.

Impact of P inputs on source-sink P dynamics of sediment along an agricultural ditch network

Phosphorus (P) loss from intensive dairy farms is a pressure on water quality in agricultural catchments. At farm scale, P sources can enter in-field drains and open ditches, resulting in transfer along ditch networks and delivery into nearby streams. Open ditches could be a potential location for P mitigation if the right location was identified, depending on P sources entering the ditch and the source-sink dynamics at the sediment-water interface. The objective of this study was to identify the right location along a ditch to mitigate P losses on an intensive dairy farm. High spatial resolution grab samples for water quality, along with sediment and bankside samples, were collected along an open ditch network to characterise the P dynamics within the ditch. Phosphorus inputs to the ditch adversely affected water quality, and a step change in P concentrations (increase in mean dissolved reactive phosphorus (DRP) from 0.054 to 0.228 mg L−1) midway along the section of the ditch sampled, signalled the influence of a point source entering the ditch. Phosphorus inputs altered sediment P sorption properties as P accumulated along the length of the ditch. Accumulation of bankside and sediment labile extractable P, Mehlich 3 P (M3P) (from 13 to 97 mg kg−1) resulted in a decrease in P binding energies (k) to < 1 L mg−1 at downstream points and raised the equilibrium P concentrations (EPC0) from 0.07 to 4.61 mg L−1 along the ditch. The increase in EPC0 was in line with increasing dissolved and total P in water, demonstrating the role of sediment downstream in this ditch as a secondary source of P to water. Implementation of intervention measures are needed to both mitigate P loss and remediate sediment to restore the sink properties. In-ditch measures need to account for a physicochemical lag time before improvements in water quality will be observed.

Landscape diversity and forest edge density regulate stream water quality in agricultural catchments

It is well known that the composition of land cover within a watershed plays a large role in regulating stream water quality. However, there remains significant uncertainty regarding the effect of spatial configuration of different types of land cover on water quality. Using periphytic algae (diatoms) as indicators of stream trophic state, we investigated the relationship between landscape configuration and water quality in a large number of watersheds (590) at varying catchment scales in Eastern Canada. Variation partitioning analysis showed that landscape configuration explained 48% of the variation in water quality. However, since the physiographic setting constrains most agricultural activities, most of the variation was attributed to the shared influence of surficial deposits, land cover and landscape configuration (34%). The results from regression models showed that the geomorphological setting of watersheds (surficial deposits and slopes) and the proportion of different land cover types (mainly forests, wetlands, crops and urban areas) have a major impact on stream water quality. Nevertheless, a few configuration metrics emerged as important factors. Landscape diversity appeared to have a negative impact on water quality, whereas forest and wetland edge densities had a positive impact. Moreover, the influence of these lanscape metrics seems to occur at certain thresholds. In areas of intensive farming, streams with a forest area that covers at least 47% of the watershed have a better water quality. Below this threshold, eutrophic and meso-eutrophic conditions are more frequent in streams and rivers. The shape and location of forested patches were also found to be relevant. Woodlands and wetlands with an edge density higher than 36m/ha and located along streams and gullies have a positive impact on water quality. For the same proportion of forest, complex patches will be more efficient filters than large regular patches. Forest edge density seems to control the extent of the interface with the agricultural sources and thus promotes the “sink” effect of forests on nutrients.

Influence of landscape properties on stream water quality in agricultural catchments in Southeastern Brazil

Changes in land cover, especially the replacement of forest by agricultural activities affect the hydrological processes of river catchments, resulting in physical and chemical compositional changes of water draining from affected basins. The aim of this study was to evaluate landscape influences at different spatial scales (catchment and riparian) on the physical and chemical composition of stream water in 15 agricultural catchments, belonging to the Corumbataí basin (Brazil). We calculated the average slope (%), average elevation (m), soil classes (%), major land use classes (%), average distance from the forest cover in relation to the hydrographic network (m), largest patch index (%) at the catchment scale and riparian zone of drainage network scale within a 30 m buffer. Water samples were collected in two seasons (dry and rainy) to characterize physical and chemical properties: turbidity, suspended solids, total nitrogen, nitrate and total phosphorus. Our results showed higher concentration of nitrate in sugarcane fields and larger amount of suspended solids and turbidity in pasture areas. We concluded that degraded and highly fragmented forests may not be effectively contributing toward the protection of aquatic ecosystems.

Nitrogen content and trends in agricultural catchments in Estonia

Several studies have shown that the stream water quality in agricultural catchments could vary according to the changes in land use, production intensities and implemented agri-environmental measures. In present study we investigated the nitrogen content and temporal dynamics in concentration and loss in small streams and catchments in Estonia for the period 1992–2011. The studied catchments represent various agricultural production areas, management practices, soil types, geology and size. A statistical analysis using the Mann Kendall (MK) test was undertaken to discern monotone trends in time series of total nitrogen (TN) and nitrate nitrogen (NO3–N) concentrations for 8 sampling sites and TN loss for five sites, for which at least a data set of 10 years was available. Additionally the partial Mann–Kendall (PMK) test has been adapted to account for the influence of water discharge to the temporal trends in TN loss in five catchments. The MK trend test revealed one statistically significant (p<0.05; two-sided test) upward trend in TN concentrations and two upward trends in NO3–N concentrations. Less significant (p<0.08) upward trend in TN content was also noted in two streams. Overall, the TN concentrations were rather high and it ranged with 90% probability from 2.3 to 8.9mgl−1 in the studied streams. The MK test revealed the statistically significant upward trend in TN loss only at the Räpu (p<0.001) and Jänijõgi (p<0.05) catchments (one-sided test). After conditioning on trends in water discharge there was only one (Räpu) statistically significant temporal upward trend in TN loss. Elevated nitrogen concentrations in three other catchments (Rägina, Vodja, Porijõgi) explain only part of the upward trend in nitrogen losses and increasing tendencies in losses could mainly be associated with upward tendency in discharge. The direct (not flow-normalised) unit-area loss of nitrogen from agricultural land reached to 63.1 and 82.5kgNha−1yr−1 in the Räpu and Jänijõgi catchments, respectively, which is higher than seen at the Rägina basin (25kgha−1yr−1) and the River Vodja catchment (21.9kgha−1yr−1). Elevated losses are typical for recent years, particularly after 2007.

Changes in water quality in agricultural catchments after deployment of wastewater treatment plant

Insufficient wastewater remediation in small communities and nonpoint source pollution are the key factors in determining the water quality of small streams in an agricultural landscape. Despite the current extensive construction of municipal wastewater treatment facilities in small communities, the level of organic substances and nutrients in the recipient catchments has not decreased in many areas. This paper analyzes the changes in the water quality of the small streams after the deployment of wastewater treatment plants that were designed to address sources of pollution from small municipalities. The analysis is based on the results from a water quality monitoring network in the small watersheds in the Czech Republic. Five rural catchments with one dominant municipal pollution source, where a wastewater treatment plant was deployed during the monitoring period, were selected according to a predefined set of criteria, from a series of 317 profiles. Basic water quality indicators were selected for the assessment: O₂, BOD-5, COD, TOC, conductivity, NH₄-N, NO₂-N, NO₃-N, PT, and PO₄-P. Results of the analysis showed that the simple deployment of the water treatment facilities at these streams often did not lead to a reduction of contamination in the streams. The expected post-deployment changes, namely, a significant and permanent reduction of stream contamination, occurred only in one catchment, whereas in the remainder of the catchments, only marginal changes or even increased concentrations of the contaminants were detected. As the critical factors that determined the efficiency of wastewater treatment were studied, the need for the consideration of the local conditions during the design of the facility, particularly regarding the size of the catchments, initial level of contamination, proper system of operation, and process optimization of the treatment facility, emerged as the important factor.

The challenge of integrating science for landscape management

‘Ecosystem restoration is now a global priority’ announced a recent editorial (Aronsen and Alexander 2013), reporting on the outcomes of the 11th Conference of the Parties (in Oct 2012) of the Convention on Biological Diversity. Large-scale programs to restore, or more sustainably manage, ecosystems exist in many countries and landscape ecologists often are at the forefront of those actively contributing their expertise. In Australia, for example, the Federal Government has invested some $6.5 billion since 1990 in a series of natural resource management and restoration programs (Hajkowicz 2009), primarily in agricultural environments to respond to the consequences of excessive clearing of native vegetation. But how do we know whether such management interventions are effective? How do we measure their impact? Is the environment in a better condition as a result of these investments? Could these restoration actions be carried out in a more effective and efficient way? These kinds of challenging questions were the stimulus for a research project in southern Australia, documented in this volume. ‘Landscape Logic’ was a four-year, nationally funded project, which set out to ‘measure the effects of past human intervention on the environment using a combination of biophysical and social evidence, and the experience of land and water managers’. It was large in scale, scope and ambition: personnel were drawn from four Universities, three state agencies, and six catchment management organisations. From the outset, the project was planned to be interdisciplinary and participatory, with scientists working alongside managers. The structure of the book reflects the priority issues identified in consultation with land managers in two study areas. Thus, Part 1. ‘Managing water quality in agricultural catchments’ relates to project components undertaken in the state of Tasmania (Chaps. 2–9), where the issue of water quality was of greatest concern. Part 2, ‘Vegetation change in rural landscapes’, relates to components in Victoria (Chaps. 10–17), where the effects of management intervention on the condition and quality of native vegetation was a priority. Part 3, ‘Integrating science and practice’, includes four chaps. (18–21) that synthesize aspects of the overall project. Two questions kept recurring as I read this book: ‘who is this written for?’ and ‘what is its purpose?’. My initial expectation was that the book would provide an array of new scientific evidence evaluating ecological outcomes of the extensive restoration and management activities undertaken in Australia over the last two decades. However, while the bulk of the chapters are centred on various research components of the project, communication of research findings is not the sole intention of the book. Rather, it documents the ‘anatomy’ of a major project, including what it set A. F. Bennett (&) School of Life & Environmental Sciences, Deakin University, 221 Burwood Highway, Burwood, VIC 3125, Australia e-mail: Andrew.Bennett@deakin.edu.au

Nitrogen retention in natural Mediterranean wetland-streams affected by agricultural runoff

Abstract. Nitrogen retention efficiency in natural Mediterranean wetland-streams affected by agricultural runoff was quantified and the effect of the temporal variability and hydrological/chemical loading was examined from March 2007 to June 2008 in two wetland-streams located in Southeast Spain. Nitrate-N (NO−3-N), ammonium-N (NH+4-N), total nitrogen-N (TN-N), total organic nitrogen-N (TON-N) and chloride (Cl−) concentrations were analyzed to calculate nitrogen retention efficiencies. These wetland-streams consistently reduced water nitrogen concentration throughout the year with higher values for NO−3-N (72.3%), even though the mean value of inflow NO−3-N concentrations was above 20 mg l−1. Additionally, they usually acted as sinks for TON-N (8.4%), but as sources for NH+4-N. Over the entire study period, the Taray and Parra wetland-streams were capable of removing on average 1.6 and 0.8 kg NO−3-N a day−1, respectively. Retention efficiencies were not affected by temperature variation. NO−3-N retention efficiency followed a seasonal pattern with the highest retention values in summer (June–September). The temporal variability for NO−3-N retention efficiency was positively and negatively explained by the hydrologic retention and the inflow NO−3-N concentration (R2adj=0.815, p&lt;0.01), respectively. No significant regression model was found for TON-N and NH+4-N. Finally, the conservation of these Mediterranean wetland-streams may help to not only improve the surface water quality in agricultural catchments, but to also achieve good ecological status for surface waters, this being the Water Framework Directive's ultimate purpose.

Water quality and the effects of different pastoral animals

Water quality in agricultural catchments tends to be worse than in forested (native or exotic) catchments. Reduced water quality tends to have significant effects on the ecosystem of streams, including increased nuisance algal and plant growth (eutrophication) associated with nutrient input, toxicity to aquatic life due to ammonia, faecal contamination, and loss of habitat or spawning areas due to sedimentation. An analysis of catchment contaminant loads from 38 studies conducted since 1975 was carried out to determine if there were differences in loads between land uses under different livestock (dairy, sheep, sheep-and-beef (mixed), deer) and non-agricultural. Significantly more N was lost from dairy catchments than catchments with other land uses, and more sediment lost from deer catchments than other catchments. Median loads of N were greatest from dairy > deer = mixed > sheep > non-agricultural; while loads of P were greatest for deer = mixed > dairy > sheep > non-agricultural; and for sediment, deer > sheep > mixed > dairy > non-agricultural. This information should be considered in catchments of mixed stock types to target the most pertinent mitigation practice for improving water quality. For example, if a stream in a catchment with deer and sheep present is choked with algae and limited by inputs of P, mitigation should focus on deer rather than sheep.

Relationships between Landscape Pattern, Wetland Characteristics, and Water Quality in Agricultural Catchments

Water quality in streams is dependent on landscape metrics at catchment and wetland scales. A study was undertaken to evaluate the correlation between landscape metrics, namely patch density and area, shape, heterogeneity, aggregation, connectivity, land-use ratio, and water quality variables (salinity, nutrients, sediments, alkalinity, other potential pollutants and pH) in the agricultural areas of a semiarid Mediterranean region dominated by irrigated farmlands (NE Spain). The study also aims to develop wetland construction criteria in agricultural catchments. The percentage of arable land and landscape homogeneity (low value of Simpson index) are significantly correlated with salinity (r(2) = 0.72) and NO(3)-N variables (r(2) = 0.49) at catchment scale. The number of stock farms was correlated (Spearman's corr. = 0.60; p < 0.01) with TP concentration in stream water. The relative abundance of wetlands and the aggregation of its patches influence salinity variables at wetland scale (r(2) = 0.59 for Na(+) and K(+) concentrations). The number and aggregation of wetland patches are closely correlated to the landscape complexity of catchments, measured as patch density (r(2) = 0.69), patch size (r(2) = 0.53), and landscape heterogeneity (r(2) = 0.62). These results suggest that more effective results in water quality improvement would be achieved if we acted at both catchment and wetland scales, especially reducing landscape homogeneity and creating numerous wetlands scattered throughout the catchment. A set of guidelines for planners and decision makers is provided for future agricultural developments or to improve existing ones.

Methods for water quality sampling and load estimation in monitoring of Norwegian agricultural catchments

Different sampling procedures are applied to monitor water quality in agricultural catchments in the Nordic countries. The need for comparing monitoring results from the Nordic countries was the incentive for establishing a project aimed at comparing estimates of nutrient losses determined using different sampling strategies. Three different sampling methods were compared in three Norwegian catchments: weekly flow-proportional composite sampling (FPCS), weekly composite sampling with temporally equidistant subsampling every second hour (TECS) and temporally equidistant weekly point sampling (PS). Differences in load estimated between the three tested sampling strategies were smaller for nitrogen than for phosphorus or suspended solids. Point sampling tended to miss some of the peaks in concentrations of phosphorus and suspended solids, particularly during flow events, causing significantly lower load estimates for phosphorus and suspended solids by point sampling compared with composite sampling strategies. Flow-proportional composite sampling gave the most reliable data for event-responsible compounds or when the predictability of peaks was low. Based on this investigation, and similar studies in the other Nordic countries, a flow-proportional sampling strategy is recommended for studies of water quality in agricultural streams.