DOI: 10.5285/c53a1f93-f64c-4d84-82a7-44038a394c59
title: Conwy catchment - spatial water chemistry dataset

description: Surface water quality data for the Conwy catchment, North Wales are presented. The data cover stream and estuary survey locations sampled manually from 2007 to 2011 at varying intervals between fortnightly and quarterly. Survey locations were selected as draining the main landscape classes in the catchment, which include upland (>300m) and lowland (<300m) environments under trees, moorland or improved agriculture. Also included are a suite of locations on the major rivers, and in the estuary. The purpose of the data is to provide support for estimating loads and testing hypotheses relating to the relationship between subcatchment properties and water quality, and the relative importance of mixing and in-stream processes in influencing downstream water quality. Streams draining peat, with high dissolved organic carbon concentrations, are well represented. Upland drainage is generally acidic, and lowland circum-neutral. The lowland rivers are not heavily contaminated with nutrients, although they show evidence of some loss of nitrates in particular. There is little industry in the catchment beyond agriculture and tourism, though there is some legacy contamination from metal mines in a small part of the catchment. Measurements are provided for major cations and anions, pH, alkalinity, DOC, Al, Fe and conductivity for most samples, with values for a wide range of trace elements for a limited number of samples.
description: Water samples were collected at 67 sites within the Conwy catchment, N. Wales. Many of the sampling sites are headwaters; some are on major tributaries or the main Conwy river. Headwater sites were selected in a manner loosely stratified by 'landscape class' formed by combining dominant land use and soils classes. However, site locations were not randomised, but all readily accessible from roads. The purpose of data collection was to 1) To help identify statistical relationships between headwater stream chemistry and catchment characteristics and 2) To provide test data for modelling stream water chemistry at downstream sites. The PEARLS/CASCADE model has been used for this purpose. In recent years the focus has been on the carbon budget, and the data may be compared with data from other experimental and survey projects within the catchment. Many sites were originally selected for acid rain research and have earlier data not included in the database. These sites were part of a wider network covering North and Mid Wales. For some sites there are additional data from sampling by other bodies, such as the Environment Agency (EA). Other Conwy sites not recorded may also have EA or other data. Samples were filtered immediately after collection through a 0.45µm cellulose nitrate filter paper. In situ measurements of pH and conductivity were taken at the same time as water samples were collected. Samples were stored below 4°C before analysis in the UKAS accredited labs in CEH Lancaster. The results from 60 determinands are presented in the dataset, including the standard suite of base cations, anions and metals. Full details of site location, field and laboratory methodology is included in the supporting documents that accompany the dataset.