This dataset is part of Integrated Hydrometric Units (IHU) of the UK. Hydrometric Areas are used to organise river flow measurement and hydrometric data collection in the UK. Hydrometric Areas are either integral river catchments having one or more outlets to the sea or tidal estuary, or they may include several contiguous river catchments having topographical similarity but separate tidal outlets. In mainland Britain they are numbered from 1 to 97 in clockwise order around the coast commencing in north east Scotland. The larger islands and groups of islands are numbered from 100-108. Ireland has a unified numbering system from 1 to 40 commencing with the River Foyle catchment and circulating clockwise; not all Irish Hydrometric Areas, however, have an outlet to the coast. Only those Hydrometric Areas covering Great Britain and Northern Ireland are included in this dataset. The boundaries between hydrometric areas correspond to catchment boundaries as digitally-derived from CEH Integrated Hydrological Digital Terrain Model (IHDTM) using a catchment definition program. It should be noticed that the Northern Ireland data are clipped to its political boundary so not every Hydrometric Area in this region is completely represented. The naming and numbering convention for the hydrometric areas in Great Britain was originally defined by the Inland Water Survey Committee (and first published in the Surface Water Year-Book of Great Britain 1936-37). For Northern Ireland the system was developed by a multi-agency working group in the 1970s (and first published in Surface Water: United Kingdom 1971-73. Note that full citations of those two publications are provided as additional information source. This dataset represent the same entities as the IHU Hydrometric Areas of the UK without Coastline, however, the outer boundaries of the units follow coastline published by the Ordnance Survey (Meridian 2), rather than the boundaries of the CEH Integrated Hydrological Digital Terrain Model. Full details about this dataset can be found at https://doi.org/10.5285/1957166d-7523-44f4-b279-aa5314163237

On site measurements of pH, conductivity and temperature for thirteen sites in the Humber catchment and three sites in the Tweed catchment within the period 1994 to 1997 as part of the Land Ocean Interaction Study project (LOIS). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were obtained using a wide neck PTFE bottle in a plastic covered bottle carrier (lowered from bridges where possible otherwise collected by immersing sample bottle by hand in the water as near the main flow as possible). pH and conductivity reading were taken using Mettler Toledo Check Mate meters and probes. Temperature readings were obtained using a PT 100 probe with a Digitron 3204 Pt meter (RS components). The measurements were carried out by members of the field sampling team at York University, as part of the Land Ocean Interaction Study (LOIS). Full details about this dataset can be found at https://doi.org/10.5285/329cbe8f-a292-4c5f-a15a-6528774dbee7

Polychlorinated biphenyls (PCB), chlorobenzenes (CB) and organochlorine pesticides (OC) data from river water collected at various sites within the Humber catchment area as part of the Land Ocean Interaction Study project (LOIS). Data were collected at regular weekly intervals and intermittently during periods of high flows. All sites were samples from early 1994 to the end of 1996 except for O12, which was sampled from November 1994 till November 1996. The sampling was carried out by the LOIS team at York University. The unfiltered samples were transported to the Institute of Terrestrial Ecology, Monks Wood, UK, where they were extracted with hexane, cleaned up by alumina column chromatography, concentrated and then analysed for CBs by Gas Chromatography-Mass Spectrometry (GC-MS) and PCBs and OCs by Gas Chromatography with Electron Capture Detection (GC-ECD). Full details about this dataset can be found at https://doi.org/10.5285/40ba6fd0-3d41-4520-8d78-cc8c893fd974