TY - JOUR
T1 - An analysis of long-term trends, seasonality and short-term dynamics in water quality data from Plynlimon, Wales
T2 - Climate Change and Macronutrient Cycling along the Atmospheric, Terrestrial, Freshwater and Estuarine Continuum - A Special Issue dedicated to Professor Colin Neal
AU - Halliday, Sarah J.
AU - Wade, Andrew J.
AU - Skeffington, Richard A.
AU - Neal, Colin
AU - Reynolds, Brian
AU - Rowland, Philip
AU - Neal, Margaret
AU - Norris, Dave
N1 - The data resource comes directly via Centre for Ecology and Hydrology core science within the Natural Environmental Research Council as does their staffing component. Funding for the analysis of the data was provided by EPSRC (Grant Number EP/G019967/1) with regard to the Reading research component. EPSRC had no further role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.
PY - 2012/9/15
Y1 - 2012/9/15
N2 - This paper examines two hydrochemical time-series derived from stream samples taken in the Upper Hafren catchment, Plynlimon, Wales. One time-series comprises data collected at 7-hour intervals over 22 months (Neal et al., 2012-this issue), while the other is based on weekly sampling over 20 years. A subset of determinands: aluminium, calcium, chloride, conductivity, dissolved organic carbon, iron, nitrate, pH, silicon and sulphate are examined within a framework of non-stationary time-series analysis to identify determinand trends, seasonality and short-term dynamics. The results demonstrate that both long-term and high-frequency monitoring provide valuable and unique insights into the hydrochemistry of a catchment. The long-term data allowed analysis of long-term trends, demonstrating continued increases in DOC concentrations accompanied by declining SO4 concentrations within the stream, and provided new insights into the changing amplitude and phase of the seasonality of the determinands such as DOC and Al. Additionally, these data proved invaluable for placing the short-term variability demonstrated within the high-frequency data within context. The 7-hour data highlighted complex diurnal cycles for NO3, Ca and Fe with cycles displaying changes in phase and amplitude on a seasonal basis. The high-frequency data also demonstrated the need to consider the impact that the time of sample collection can have on the summary statistics of the data and also that sampling during the hours of darkness provides additional hydrochemical information for determinands which exhibit pronounced diurnal variability. Moving forward, this research demonstrates the need for both long-term and high-frequency monitoring to facilitate a full and accurate understanding of catchment hydrochemical dynamics.
AB - This paper examines two hydrochemical time-series derived from stream samples taken in the Upper Hafren catchment, Plynlimon, Wales. One time-series comprises data collected at 7-hour intervals over 22 months (Neal et al., 2012-this issue), while the other is based on weekly sampling over 20 years. A subset of determinands: aluminium, calcium, chloride, conductivity, dissolved organic carbon, iron, nitrate, pH, silicon and sulphate are examined within a framework of non-stationary time-series analysis to identify determinand trends, seasonality and short-term dynamics. The results demonstrate that both long-term and high-frequency monitoring provide valuable and unique insights into the hydrochemistry of a catchment. The long-term data allowed analysis of long-term trends, demonstrating continued increases in DOC concentrations accompanied by declining SO4 concentrations within the stream, and provided new insights into the changing amplitude and phase of the seasonality of the determinands such as DOC and Al. Additionally, these data proved invaluable for placing the short-term variability demonstrated within the high-frequency data within context. The 7-hour data highlighted complex diurnal cycles for NO3, Ca and Fe with cycles displaying changes in phase and amplitude on a seasonal basis. The high-frequency data also demonstrated the need to consider the impact that the time of sample collection can have on the summary statistics of the data and also that sampling during the hours of darkness provides additional hydrochemical information for determinands which exhibit pronounced diurnal variability. Moving forward, this research demonstrates the need for both long-term and high-frequency monitoring to facilitate a full and accurate understanding of catchment hydrochemical dynamics.
KW - High frequency monitoring
KW - Carbon
KW - Nitrogen
KW - Plynlimon
KW - Time-series analysis
KW - Diurnal cycles
U2 - 10.1016/j.scitotenv.2011.10.052
DO - 10.1016/j.scitotenv.2011.10.052
M3 - Article
SN - 0048-9697
VL - 434
SP - 186
EP - 200
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -