Agricultural Catchments Research Articles

Hydrochemical dynamics of stream following rainfall events at agricultural catchments in New Zealand

One of the prerequisites for efficiently managing lake water quality is reliable data regarding the quantity and quality of inflows water, mainly the export of nutrients from the catchment area during rainfall events. We investigated the dynamic characteristics of hydrochemicals concerning rainfall events in agricultural stream waters flowing into eutrophic lakes situated on the North Island’s central plateau of New Zealand. We utilized isotopic composition of water (δ2H-H2O and δ18O-H2O) and nitrate (δ15N-NO3- and δ18O-NO3-) along with high-frequency hydrochemical data for source identification of water and nitrate during a drought period (2020). Our findings indicate that it is essential to initially grasp the fundamental mechanisms associated with rainfall events to formulate effective strategies for minimizing nutrient losses. The methodology outlined in this research integrates stable isotope hydrology with water quality monitoring initiatives, facilitating the understanding and managing the primary governing mechanisms behind diverse contaminant losses from land to adjacent water bodies, explicitly focusing on nitrates. This approach establishes a framework that can assist in devising measures for water quality improvement capable of anticipating the repercussions of substantial rainfall events more effectively.

Assessment of nitrogen budget in detailed spatial pattern using high precision modeling approach with constructed accurate agricultural behavior

Changes in the nitrogen cycle due to fertilizer use can cause severe environmental pollution, particularly groundwater pollution, and threaten biosphere integrity. There are many difficulties and limitations in assessing groundwater pollution and a detailed nitrogen budget in an agricultural catchment. Previous methodologies have failed in an accurate assessment of the nitrogen budget in detailed spatial patterns. Herein, we designed a new modeling approach to assess the nitrogen budget using detailed spatial patterns in an agricultural catchment in the Nara Basin. We revised the Soil and Water Assessment Tool file output format, added the results for river nutrient concentrations and ammonia volatilization to the original output file. In this study, we calibrated and validated crop harvests, paddy evapotranspiration, streamflow, and river water concentrations of nitrate–nitrogen and total nitrogen to improve model accuracy as much as possible. Among them, data for evapotranspiration was obtained from a newly released Landsat dataset. The results showed that the amount of nitrogen leaching in rice paddies was 42 kg/ha, accounting for 65 % of total leaching in the study catchment. Cambisols and Fluvic Gleysols were prone to denitrification, and nitrogen leaching or denitrification occurred relatively more readily in low-slope areas. Furthermore, a detailed analysis of nitrogen cycle processes with high spatial precision indicates that areas with severe surface water pollution may also exhibit significant groundwater pollution. Our findings provide new solutions for assessing the nitrogen budget and groundwater pollution in catchments.

Importance of different factors for modeling nitrate transport and retention in a tile-drained agricultural catchment with distance-based generalized sensitivity analysis

Modeling of nitrate transport and retention in agricultural land use areas provides useful information to support water quality assessment and management. The accuracy and precision of model simulations are highly dependent on model input factors for which the appropriate values are generally difficult to determine and from which various uncertainties are induced into the modeling procedure. In this study, we applied a Distance-based Generalized Sensitivity Analysis (DGSA) to a high-resolution (25 × 25 m) nitrate transport and retention model for a tile-drained agricultural catchment (4.4 km2) to investigate the extent to which model input factors affect the spatially distributed nitrate retention. The input factors included the nitrate leaching from the root zone, the partitioning of nitrate into tile drainage and groundwater flux, the groundwater flux out of the catchment, the hydrogeological properties, and the denitrification rates in groundwater. The DGSA results were examined in both spatially lumped and distributed perspective. We found that the partitioning of nitrate into tile drainage and groundwater flux was the most important factor for modeling nitrate retention while the hydrogeological properties were secondary but also important. Conversely, the nitrate leaching from the root zone and denitrification rates in groundwater were noninfluential. By increasing the resolution of the DGSA analysis from catchment to model pixel, we found that input factors noninfluential on catchment scale were influential on pixel scale in discrete areas, and, as a general take-home-message, input factors influential on nitrate retention in at least 25 % of the model pixels were sensitive on catchment scale as well. Improved understanding of sensitivity of modelling nitrate retention may help the modelers and water managers to decide which input factors to prioritize in the modelling and data collection to improve the accuracy and precision of the model responses.

The Impact of Various Types of Cultivation on Stream Water Quality in Central Poland

Agricultural practices have a significant impact on stream water quality in rural landscapes; however, there is still little empirical evidence of how different types of cultivation alter the hydrochemistry of running water. Thus, the current study explored the spatial dynamics of selected ion concentrations and their land cover dependence in lowland agricultural catchments. From November 2021 to October 2022, water samples were collected from 30 sites located across small tributaries of the rivers Bzura, Pilica, and Radomka for chemical analysis of their NO3, NO2, NH4, Ca, Mg, K, Na, As, Ba, Sr, and V concentrations. The results indicated a clear spatial heterogeneity of water quality, related to lithology and dominant land cover evaluated with the CORINE Land Cover 2018 dataset. Overall, sites representing agricultural land promoted increased concentrations of major and trace elements, while those with pepper cultivation were additionally contaminated with NO3 and NO2. The correlation performance for nitrogen compounds was the highest for narrower buffer zones, which was not documented for major and trace elements, which were linked more strongly with land cover at larger scales. Such new insights into the water quality dynamics of lowland agricultural catchments, being a simultaneous reflection of lithology, agricultural practices, and several municipal impacts, have significant implications for appropriate water management in rural landscapes.

Soil erosion, sediment sources, connectivity and suspended sediment yields in UK temperate agricultural catchments: Discrepancies and reconciliation of field-based measurements

Robust understanding of the fine-grained sediment cascades of temperate agricultural catchments is essential for supporting targeted management for addressing the widely reported sediment problem. Within the UK, many independent field-based measurements of soil erosion, sediment sources and catchment suspended sediment yields have been published. However, attempts to review and assess the compatibility of these measurements are limited. The data available suggest that landscape scale net soil erosion rates (∼38 t km−2 yr−1 for arable and ∼26 t km−2 yr−1 grassland) are comparable to the typical suspended sediment yield of a UK catchment (∼44 t km2 yr−1). This finding cannot, however, be reconciled easily with current prevailing knowledge that agricultural topsoils dominate sediment contributions to watercourses, and that catchment sediment delivery ratios are typically low. Channel bank erosion rates can be high at landscape scale (27 km−2 yr−1) and account for these discrepancies but would need to be the dominant sediment source in most catchments, which does not agree with a review of sediment sources for the UK made in the recent past. A simple and robust colour-based sediment source tracing method using hydrogen peroxide sample treatment is therefore used in fifteen catchments to investigate their key sediment sources. Only in two of the catchments are eroding arable fields likely to be important sediment sources, supporting the alternative hypothesis that bank erosion is likely to be the dominant source of sediment in many UK catchments. It is concluded that the existing lines of evidence on the individual components of the fine sediment cascade in temperate agricultural catchments in the UK are difficult to reconcile and run the risk of best management interventions being targeted inappropriately. Recommendations for future research to address paucities in measured erosion rates, sediment delivery ratios and suspended sediment yields, validate sediment source fingerprinting results, consider the sources of sediment-associated organic matter, and re-visit soil erosion and sediment cascade model parameterisation are therefore made.

Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination

Once released into the environment, herbicides can move through soil or surface water to streams and groundwater. Filters containing adsorbent media placed in fields may be an effective solution to herbicide loss in the environment. However, to date, no study has investigated the use of adsorbent materials in intervention systems at field-scale, nor has any study investigated their optimal configuration. Therefore, the aim of this paper was to examine the efficacy of low-cost, coconut-based activated carbon (CAC) intervention systems, placed in streams and tributaries, for herbicide removal. Two configurations of interventions were investigated in two agricultural catchments and one urban area in Ireland: (1) filter bags and (2) filter bags fitted into polyethylene pipes. Herbicide sampling was conducted using Chemcatcher® passive sampling devices in order to identify trends in herbicide exceedances at the sites, and to quantifiably assess, compare, and contrast the efficiency of the two intervention configurations. While the Chemcatcher® passive sampling devices are capable of analysing eighteen different acid herbicides, only six different acid herbicides (2,4-D, clopyralid, fluroxypyr, MCPA, mecoprop and triclopyr) were ever detected within the three catchment areas, which were also the only acid herbicides used therein. The CAC was capable of complete herbicide removal, when the water flow was slow (0.5–1 m3 s−1), and the interventions spanned the width and depth of the waterway. Overall, the reduction in herbicide concentrations was better for the filter pipes than for the filter bags, with a 48% reduction in detections and a 37% reduction in exceedances across all the sampling sites for the filter pipe interventions compared to a 13% reduction in the number of detections and a 24% reduction in exceedances across all sampling sites for the filter bag interventions (p < 0.05). This study demonstrates, for the first time, that CAC may be an effective in situ remediation strategy to manage herbicide exceedances close to the source, thereby reducing the impact on environmental and public health.

Quantification of agricultural best management practices impacts on sediment and phosphorous export in a small catchment in southeastern Sweden

Agricultural activities contribute to water pollution through sediments and nutrient export, negatively affecting water quality and aquatic ecosystems. However, implementing best management practices (BMPs) could help control sediments and nutrient losses from agricultural catchments. This study used the Soil Water Assessment Tool (SWAT) model to assess the effectiveness of four BMPs in reducing sediment and phosphorus export in a small agricultural catchment (33 km2) in southeastern Sweden. The SWAT model was first evaluated for its ability to simulate streamflow, sediment load, and total phosphorous load from 2005 to 2020. Then, the calibrated parameters were used to simulate the agricultural BMP scenarios by modifying relevant parameters. The model performed satisfactorily during calibration and validation for streamflow (NSE = 0.80/0.84), sediment load (NSE = 0.67/0.69), and total phosphorous load (NSE = 0.61/0.62), indicating its suitability for this study. The results demonstrate varying effects of BMP implementation on sediment and phosphorus (soluble and total) export, with no significant change in streamflow. Filter strips were highly effective in reducing sediment (−32%), soluble phosphorus (−67%), and total phosphorous (−66%) exports, followed by sedimentation ponds with −35%, −36%, and −50% reductions, respectively. Grassed waterways and no-tillage were less impactful on pollutant reduction, with grassed waterways showing a slight increase (+4%) in soluble phosphorus and no-tillage having a minimal effect on sediment (−1.3%) and total phosphorus (−0.2%) export. These findings contribute to the ongoing efforts to mitigate sediment and nutrient pollution in Swedish agricultural areas, thereby supporting the conservation and restoration of aquatic ecosystems, and enhancing sustainable agricultural practices.

From the Ground Up

This paper explores the potential of GIS-based analyses of legacy survey data to inform discussions of settlement patterning, demographic change and the social organisation of agricultural production in the ancient Mediterranean. Legacy survey data represent an important body of evidence for understanding the development of past settlement systems, while their digitisation presents opportunities for novel quantitative and spatial analyses. By combining data from three contiguous intensive surveys from the Mirabello area of eastern Crete, this study investigates trajectories of demographic change and subsistence practice in the Early Iron Age (EIA) and Archaic periods (ca. 1200–550 bc), utilising GIS-based modelling of minimal agricultural catchments, and considering the relationships between communities over multiple geographic scales. This analysis highlights a transition away from clusters of small, demographically interdependent hamlets and villages in the earlier part of the EIA, toward the consolidation of nucleated population centres by the Archaic. The investigation of these developments contributes to our understanding of the scale, territorial control and management of agricultural hinterlands in the formative stages of the Greek poleis. The methods employed have wider relevance for the study of agricultural systems in the ancient Mediterranean, and highlight the important ongoing contributions of legacy survey data to theorising ancient subsistence economies.

Contrasting change trends in dry and wet nitrogen depositions during 2011 to 2020: Evidence from an agricultural catchment in subtropical Central China

Over the past decade, China has experienced a decline in atmospheric reactive nitrogen (Nr) emissions. Given that China's subtropical region is a significant nitrogen (N) deposition hotspot, it is essential to accurately quantify the ten-year variations in dry and wet N depositions in the context of reductions in atmospheric Nr emissions. Here, we evaluated the spatiotemporal variation in N deposition on forest, paddy field and tea field ecosystems in a typical subtropical agricultural catchment from 2011 to 2020. Our findings indicated a significant decrease in total N deposition in both the tea field ecosystem (41.5–30.5 kg N ha−1) and the forest ecosystem (40.8–25.7 kg N ha−1) (P < 0.05), but no significant change in the paddy field ecosystem (29.3–32.9 kg N ha−1). Specifically, dry N deposition exhibited significant declines except in the paddy field ecosystem, whereas wet N deposition had no significant change. The reduction in total oxidized and reduced N depositions in forest and tea field ecosystems is attributed to the decrease in NOx and NH3 emissions. Additionally, The ratio of NHx deposition to total N deposition all exceeded 0.5 in three ecosystems and the NHx/NOy ratio had an increasing trend (P < 0.05) in the paddy field, indicating that reactive N emissions from agricultural sources were the primary contributor to overall N deposition. Our study emphasizes that despite the decreasing trend in N deposition, it still exceeds the critical loads of natural ecosystems and requires stringent N emissions control, particularly from agricultural sources, in the future.

Hybrid Extreme Gradient Boosting and Nonlinear Ensemble Models for Suspended Sediment Load Prediction in an Agricultural Catchment

Hybrid Extreme Gradient Boosting and Nonlinear Ensemble Models for Suspended Sediment Load Prediction in an Agricultural Catchment

Seasonal variations of vegetative indices and their correlation with evapotranspiration and soil water storage in a small agricultural catchment

Seasonal variations of vegetative indices and their correlation with evapotranspiration and soil water storage in a small agricultural catchment

Farm dam accounting for healthy and safe agricultural catchments

ABSTRACT Farm dams are essential infrastructure for many farming operations, including livestock watering and crop irrigation. With demand for food increasing, many farmers are looking to capture, store and use more runoff to achieve higher yields under worsening climate extremes. The aim of this article is to advance understanding of farm dams in catchments and the current tools for accounting for them, providing an opportunity to consider a new runoff storage accounting framework to support integrated policy. The Australian dam management setting is provided for context. A longitudinal cohort survey of 254 South Australian farmers provides a snapshot of farmer perceptions of dams and dam management behaviours. Farmers express increasing concern about the future availability of water, how much is allocated to the environment and how this is accounted for. Whilst the field of IWRM and others have integrated disciplines for improved water decision-making, so far there has been limited attention to how to incentivise improved farm dam management through links to farm accounting and business. This study proposes a preliminary framework for assisting dam decision-making across scales to support the health and safety of environments and communities.

Farming and feasting during the Bronze Age–Iron Age transition in Britain (ca. 900–500 bce): multi-isotope evidence for societal change

The Late Bronze Age saw the rise of a new site type in southern Britain, commonly termed a midden. These vast monumental mounds, some comprising tens of thousands of artefacts/ecofacts dominated by animal bone and ceramics, signal a societal refocus towards agricultural intensification and communal feasting on a grand scale. These sites point to agricultural produce being the mainstay of the economy, with bronze having a reduced social and economic importance. This likely created new regimes of managing landscapes and livestock and new networks and agricultural catchments anchored on the sites. Major questions remain surrounding the strategies employed to enhance agricultural productivity, how landscapes and livestock were managed, and how different sites and regions met these challenges at a time of climatic deterioration. This article employs multi-isotope analyses on domestic and wild fauna to address these questions. It presents carbon, nitrogen, and sulfur (δ13C, δ15N, and δ34S, respectively) isotope analyses on 235 animals from 6 midden sites in 2 major regions of midden accumulation: the Vale of Pewsey in Wiltshire and the Thames Valley. The results demonstrate distinct differences in approaches to maximising agricultural productivity, with varied strategies apparent at a site, species, and regional level. Some sites, such as Potterne and Runnymede, clearly drew domestic fauna from a wide catchment where wide-ranging management and foddering regimes were employed. Other sites, such as East Chisenbury, had a more restricted catchment but a tightly controlled, intensive management regime. These data provide new insights into regional responses to the reorganisation of the economy, landscape use, and developing agricultural networks during the Bronze Age–Iron Age transition in Britain, revealing dynamic and evolving societal change.

Looking back to move forward: Restoring vegetated canals to meet missing Water Framework Directive goals in agricultural basins

Nitrate pollution and eutrophication remain pressing issues in Europe regarding the quality of aquatic ecosystems and the safety of drinking water. Achieving water quality goals under the Water Framework Directive (WFD) has proven to be particularly challenging in agricultural catchments, where high nitrate concentrations are the main reason for the failure of many water bodies to meet a good ecological status. Canals and ditches are common man-made features of irrigated and drained landscapes and, when vegetated, have recently been identified as denitrification hotspots.By combining experimental data and GIS-based upscaling estimation, the potential capacity of the canal network to reduce nitrate loads was quantified in several scenarios differing in the level of nitrate pollution and in the extent of the canal network length where conservative management practices are implemented. The analysis was carried out in the irrigated lowlands of the Po River basin, which is the largest hydrographic system in Italy and a global hotspot for nitrogen inputs and eutrophication.Scenario simulations showed that maintaining aquatic vegetation in at least 25 % of the canal network length, selecting sites with high nitrate availability (>2.4 mg N L−1), would promote a greater potential for permanent N removal. The increased denitrification capacity would meet the load reduction target required to achieve a WFD good ecological status in waters draining into the Adriatic Sea during the spring-summer months, when the eutrophication risk is higher. Promoting denitrification in the canal network by postponing the mowing of in-stream vegetation to the end of the growing season could be an effective mitigation strategy to improve water quality in agricultural basins and contribute to achieving the WFD goals.

The Water Flow Regime in the Weir Area for Vascular and Rush Plant Species Composition

The hydrotechnical construction, damming up the riverbed, creates two zones of hydraulic conditions, which affect the water discharge and sediment transport routes, as well as plant species composition, as a habitat answer to the hydraulic regime. This study examined the diversity of the vascular and rush plant species upstream and downstream of the weir. The Świder River, a small lowland river in Central Poland, was chosen as a study area. An examined river reach was located at 21 + 340 kilometers of the Świder River. Vegetation properties, plant species, and granulometric fraction composition were recognized at chosen cross-sections along the riverbed where specific hydraulic conditions could be met. The spatial distribution of vortices, smooth or rapid flow areas, and velocity pulsations influence the biotic environment, thereby affecting the species composition, quantity, and plant diversity. In the headwater zone, an environment more favorable to grain accumulation could be met, which was mixed with organic components in an agricultural catchment area. This phenomenon leads to creating favorable conditions for increased biodiversity. The present study demonstrated that small weirs could positively affect the composition of vascular and rush plants.

High methane emissions as trade-off for phosphorus removal in surface flow treatment wetlands

Constructed wetlands (CW) treating runoff from agricultural catchments reduce the nutrient load of water, however, they can also be significant sources of greenhouse gases, especially methane (CH4). We simultaneously assessed CH4 emission potentials and phosphorus (P) removal efficiency in a 0.45 ha in-stream surface flow CW to determine the main drivers of CH4 emissions, and to analyze the temporal dynamics of CH4 emissions and P removal during an almost 4-year period. The TP (total phosphorus) removal efficiency had a clear seasonal dynamic, with the highest removal occurring during summer and early autumn (monthly average 60.5%), when the flow rate was lowest and water residence time longest. Due to increasing sedimentation and related anaerobic conditions, the mean hourly CH4 emissions for each year demonstrated an increasing trend over the years: from 88 µg CH4-C m−2 h−1 in 2018–2505 µg CH4-C m−2 h−1 in 2021. There was a clear seasonality in CH4 emissions: up to 90% of CH4 fluxes occurred during the warm period (from May to October). We assume that maintenance of treatment wetlands is essential and predominantly regular removal of aboveground vegetation at the second half of the growing season would decrease CH4 emissions. Nevertheless, due to the P saturation in sediments, regular sediment removal in the long term is also necessary.

Mitigating runoff nitrate loss from soil organic nitrogen mineralization in citrus orchard catchments using green manure.

Nitrate-nitrogen (NO3--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 NO3--N loss, compared to cropland. To promote sustainable N fertilizer management, it is crucial to identify the sources of runoff NO3--N loss in citrus orchards catchments. Particularly, we poorly know the sources of NO3--N and the mitigation mechanisms in these areas, which are highly polluted with NO3--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 NO3--N loss, we used the dual isotope tracer method (δ15N and δ18O of NO3-) to identify the sources of NO3--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 NO3--N loss, and soil N mineralization potential (0.65⁎⁎⁎) and rate (0.54⁎⁎⁎) were the key factors impacting NO3--N loss. Interestingly, organic manure significantly increased 29.0% of NO3--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 NO3--N loss (-12.4%). Our study highlights the critical role of regulating SON mineralization in controlling NO3--N pollution in surface waters in citrus orchard catchments.

Water security and agricultural systems in the Galapagos Islands: vulnerabilities under uncertain future climate and land use pathways

The Galapagos Islands, a hotspot of ecological richness, face challenging climatic and development conditions which undermine regional water security. Yet, the way by which these conditions may change in the future is highly uncertain. In this study, we applied for the first time an uncertainty-based approach in the Galapagos Islands to understand thresholds and potential scenarios of risks to water security of agricultural catchments in the Galapagos Island. We applied a water systems model to the agricultural catchments as well as climate and land use scenarios to estimate physical changes in water availability and implications for drought and extreme flow thresholds. Our results highlight the key role of baseflow and its important sensitivity to precipitation changes in determining water security states in the Islands. In fact, a decrease in just about 25% of total water flows, from historical conditions, in the Islands would drive drought conditions resembling those of the emergency state of 2016. We also note that under a land use scenario which promotes sustainable practices, the robustness of the Islands to climate variations increases. Our study then provides the basis for an application of uncertainty-based approaches to enhance resilience of the agricultural water systems as well as other systems. Our results also emphasize the need to design flexible and comprehensive policies in the water, agricultural and interconnected sectors which consider the interlinkages of climate with other social and economic variables.

Spatial and seasonal variability of sub–daily water temperature dynamics in the lowland agricultural catchment of the Wkra River

Spatial and seasonal variability of sub–daily water temperature dynamics in the lowland agricultural catchment of the Wkra River

Response of microplastic occurrence and migration to heavy rainstorm in agricultural catchment on the Loess plateau

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.