River water quality trends and increased dairying in Southland, New Zealand

2003 ◽  
Vol 37 (2) ◽  
pp. 323-332 ◽  
Author(s):  
Keith D. Hamill ◽  
Graham B. McBride
Keyword(s):  
Water Quality ◽  
New Zealand ◽  
River Water ◽  
River Water Quality ◽  
Water Quality Trends

scholarly journals An approach for decomposing river water-quality trends into different flow classes

2021 ◽  
Vol 755 ◽  
pp. 143562
Author(s):  
Qian Zhang ◽  
James S. Webber ◽  
Douglas L. Moyer ◽  
Jeffrey G. Chanat
Keyword(s):  
Water Quality ◽  
River Water ◽  
River Water Quality ◽  
Water Quality Trends

Estimating river water-quality trends under different flow conditions

2021 ◽  
Author(s):  
Qian Zhang ◽  
James Webber ◽  
Douglas Moyer ◽  
Jeffrey Chanat
Keyword(s):  
Water Quality ◽  
River Water ◽  
Total Nitrogen ◽  
Nitrogen Concentration ◽  
High Flow ◽  
River Water Quality ◽  
Low Flow ◽  
Flow Conditions ◽  
Particulate Nitrogen ◽  
Water Quality Trends

<p>A number of statistical approaches have been developed to quantify the overall trend in river water quality, but most approaches are not intended for reporting separate trends for different flow conditions. We propose an approach called FN<sub>2Q</sub>, which is an extension of the flow-normalization (FN) procedure of the well-established WRTDS (“Weighted Regressions on Time, Discharge, and Season”) method. The FN<sub>2Q</sub> approach provides a daily time series of low-flow and high-flow FN flux estimates that represent the lower and upper half of daily riverflow observations that occurred on each calendar day across the period of record. These daily estimates can be summarized into any time period of interest (e.g., monthly, seasonal, or annual) for quantifying trends. The proposed approach is illustrated with an application to a record of total nitrogen concentration (632 samples) collected between 1985 and 2018 from the South Fork Shenandoah River at Front Royal, Virginia (USA). Results show that the overall FN flux of total nitrogen has declined in the period of 1985–2018, which is mainly attributable to FN flux decline in the low-flow class. Furthermore, the decline in the low-flow class was highly correlated with wastewater effluent loads, indicating that the upgrades of treatment technology at wastewater treatment facilities have likely led to water-quality improvement under low-flow conditions. The high-flow FN flux showed a spike around 2007, which was likely caused by increased delivery of particulate nitrogen associated with sediment transport. The case study demonstrates the utility of the FN<sub>2Q</sub> approach toward not only characterizing the changes in river water quality but also guiding the direction of additional analysis for capturing the underlying drivers. The FN<sub>2Q</sub> approach (and the published code) can easily be applied to widely available river monitoring records to quantify water-quality trends under different flow conditions to enhance understanding of river water-quality dynamics. <span>(Journal article: https://doi.org/10.1016/j.scitotenv.2020.143562; R code and data release: https://doi.org/10.5066/P9LBJEY1).</span></p>

scholarly journals River water quality changes in New Zealand over 26 years: response to land use intensity

2017 ◽  
Vol 21 (2) ◽  
pp. 1149-1171 ◽  
Author(s):  
Jason P. Julian ◽  
Kirsten M. de Beurs ◽  
Braden Owsley ◽  
Robert J. Davies-Colley ◽  
Anne-Gaelle E. Ausseil
Keyword(s):  
Water Quality ◽  
Land Use ◽  
New Zealand ◽  
River Water ◽  
River Water Quality ◽  
Land Use Intensity ◽  
Land Disturbance ◽  
Areal Coverage ◽  
Legacy Nutrients ◽  
Intensively Managed

Abstract. Relationships between land use and water quality are complex with interdependencies, feedbacks, and legacy effects. Most river water quality studies have assessed catchment land use as areal coverage, but here, we hypothesize and test whether land use intensity – the inputs (fertilizer, livestock) and activities (vegetation removal) of land use – is a better predictor of environmental impact. We use New Zealand (NZ) as a case study because it has had one of the highest rates of agricultural land intensification globally over recent decades. We interpreted water quality state and trends for the 26 years from 1989 to 2014 in the National Rivers Water Quality Network (NRWQN) – consisting of 77 sites on 35 mostly large river systems. To characterize land use intensity, we analyzed spatial and temporal changes in livestock density and land disturbance (i.e., bare soil resulting from vegetation loss by either grazing or forest harvesting) at the catchment scale, as well as fertilizer inputs at the national scale. Using simple multivariate statistical analyses across the 77 catchments, we found that median visual water clarity was best predicted inversely by areal coverage of intensively managed pastures. The primary predictor for all four nutrient variables (TN, NOx, TP, DRP), however, was cattle density, with plantation forest coverage as the secondary predictor variable. While land disturbance was not itself a strong predictor of water quality, it did help explain outliers of land use–water quality relationships. From 1990 to 2014, visual clarity significantly improved in 35 out of 77 (34∕77) catchments, which we attribute mainly to increased dairy cattle exclusion from rivers (despite dairy expansion) and the considerable decrease in sheep numbers across the NZ landscape, from 58 million sheep in 1990 to 31 million in 2012. Nutrient concentrations increased in many of NZ's rivers with dissolved oxidized nitrogen significantly increasing in 27∕77 catchments, which we largely attribute to increased cattle density and legacy nutrients that have built up on intensively managed grasslands and plantation forests since the 1950s and are slowly leaking to the rivers. Despite recent improvements in water quality for some NZ rivers, these legacy nutrients and continued agricultural intensification are expected to pose broad-scale environmental problems for decades to come.

scholarly journals River water quality changes in New Zealand over 26 years (1989–2014): Response to land use and land disturbance

2016 ◽  
Author(s):  
Jason P. Julian ◽  
Kirsten M. de Beurs ◽  
Braden Owsley ◽  
Robert J. Davies-Colley ◽  
Anne-Gaelle E. Ausseil
Keyword(s):  
Water Quality ◽  
Land Use ◽  
New Zealand ◽  
River Water ◽  
River Water Quality ◽  
Point Sources ◽  
Diffuse Pollution ◽  
Sediment Runoff ◽  
Nutrient Mobilization ◽  
Land Disturbance

Abstract. River water quality reflects land use in the catchment (mobilizing diffuse pollution) as well as point source discharges. In New Zealand (NZ) diffuse pollution vastly outweighs point sources which have largely cleaned up over many decades. Because NZ has good geospatial data on physiographic variables, land cover and agricultural statistics, and time series on water quality at the national scale over several decades, the country is a natural laboratory for investigating water quality response to land use/disturbance and associated diffuse pollution "pressures". We interpreted water quality state and trends for the 26 years from 1989 and 2014 in the National Rivers Water Quality Network (NRWQN), consisting of 77 sites on 35 mostly large river systems with an aggregate catchment amounting to half of NZ's land area. To characterize water quality pressures, we used multiple land use datasets spanning 1990–2012, plus recently-developed 8-day land-disturbance datasets using MODIS imagery. Current state and directions of change in visual clarity and nitrate-nitrite-nitrogen provide a particularly valuable summary of impact, respectively from mobilization of fine particulate matter and soluble nutrients. We show that the greatest impact on river water quality in NZ over the 1989–2014 period is high-producing pastures with their high nutrient inputs to support high densities of livestock. While land disturbance was not itself a strong predictor of water quality, it did help explain outliers of land use-water quality relationships, especially those with large areas of plantation forest. Plantation forestry was strongly associated with water quality impacts, particularly on visual clarity and particulate nutrients when land disturbed for harvesting generated sediment runoff and nutrient mobilization. In all, our study demonstrates how interdisciplinary combinations of expertise including geospatial analysis, land management, remote-sensing, and water quality can advance understanding of broad-scale and long-term impacts of land use change on river water quality.

Using historical data to identify future water quality trends at a regional scale

2020 ◽  
Author(s):  
Anna Lintern ◽  
Natalie Kho ◽  
Danlu Guo ◽  
Shuci Liu ◽  
Clement Duvert
Keyword(s):  
Climate Change ◽  
Water Quality ◽  
River Water ◽  
Historical Data ◽  
River Water Quality ◽  
Quality Deterioration ◽  
Droughts And Floods ◽  
Extreme Hydrological Events ◽  
Water Quality Trends ◽  
Water Quality Deterioration

<p>Using historical data to identify future water quality trends</p><ol><li>Lintern</li> <li>Kho</li> <li>Guo</li> <li>Liu</li> <li>Duvert</li> </ol><p> </p><p>Climate change is expected to have a severe impact on water resources management in Australia. This is expected to lead to increasing frequency in extreme hydrological events such as droughts and floods, which will in turn contribute to higher risks of bushfires, fish kills, and water shortage for both humans and the environment. The potential impacts of these climate-change-induced extreme events on the quantity of water available to humans and the environment are relatively well understood. However, we have little understanding of the effect on the water quality of Australian rivers. This project aims to start filling this gap in our understanding.</p><p>Our key objectives are:</p><p>(1) to identify how extreme hydrological events such as droughts and floods have affected river water quality over the last two decades, and explore how spatially variable these impacts have been across the Australian continent.</p><p>(2) to use these past observations as a basis to predict how river water quality will be affected by climate change across the continent, and identify the locations within Australia that will be most vulnerable to water quality deterioration in the near future.</p><p>There is a wealth of historical water quality data for each state in Australia, but these datasets have not yet been investigated systematically to develop a nation-wide understanding of water quality patterns. We believe that only a continental-scale understanding of the response of river water quality to extreme hydrological events will allow for the development of robust predictive models of climate change impacts on water quality. Knowing the potential hotspots for future water quality deterioration will be a key step towards identifying priorities for catchment planning and management.</p><p>In this poster, we will present the preliminary findings of this project by detailing the spatial variability in the impact of hydrological events on water quality across the state of Victoria in South-East Australia.</p>

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