7Th Institute of ) Hydrology Report No. 128 The w ate r quality of the Twe e d and its tributarie s N atural Env ironm ent Re se arch Coun c il á R ep o r t Na 12 8 Th e w a ter q ua lity of the Tw eed a nd its tr ibuta r ies A J R o bs o n, C Nea l Inst it ut e of H y dro logy, Wallingfo rd J C Cu r r ie, W A Vir tu e, A R ing ro s e Tw eed Riv er Pu r if icat io n Bo ard , Galashie ls Tweed River Purification Bo ard In stitute of Hydrology Burnbrae Crow mars h Giffo rd Mos silee Road Wallin gfo rd Galashiels Oxfo rdsh ire TD 1 1NF OX10 8BB 0 Co py r ight I nst it ut e of H yd r o logy 19 9 6 ISBN 0 9 4 8 54 0 7 4 5 1H Rep o r t N o . 12 8 p u b lished by t he Inst it ut e of H y dro logy Feb r u a r y 19 9 6 LemS British Library Cataloguing-in-Publication Data A catalogue reco rd for this book is available from the British Library E x ecu tive s u m m a ry This report Ls based on extensive records collected data. Point inputs are important sources of many by the Tweed River Purifi cation Board and details determinands (e.g. phosphate, most metals and results from a regional analysis of water quality in many micro-organics) and, in some cases, make a the Tweed river catchment. The work is part of the significant contribution to the overall riverine lo-ad rivers component of the NERC Land Occ-an Interac- (e.g. copper and lead). Diff use agricultural sources tion Study which seeks to understand and quantify are particularly important in lowland arable areas the movement of chemicals from the rivers to the (e.g. fiir nitrate, phosphate and micro-organics). In sea. The report emphasises the msearch value of addition, widespread geological sources contribute routine water quality data as collected by the River to krads of metaLs such as iron and zinc. Regional Purification lloards and the National Rivers Author- remis sion analysis suggests that spatial variations ity. These data are a national resource, far more can be formally linked to land use and other extensive than specifi c research programmes can factors. provide. However, making grxxl use of such vast information resources is not easy. There are very Sewage effl uent is the most signifi cant source of few publications describing broad water quality many pollutant chemicals in the Tweed river basin. characteristics at the regional scale: this report The quality of sewage effl uent is regulated by attempts to redress this imbalance. Simple analytical consent conditions. Around 87% of sewage treat- and graphical tools have been developed to aid ment works currently meet consent conditio ns and regional description and here they are used to this figure is rising. Biochemical oxygen demand, provide a regional overview for the Tweed river nitrate, total ammonia, chloride and phosphate are basin. high in sewage effl uent relative to background river concentrations. This is due to the biodegrad- The Tweed is a rural river system in the eastern able load from faecal matter in domestic effl uent Scottish Borders south of Edinburgh. The area is plus trade effl ent from industries such as food agricultural, ranging from upland areas of moorland processing and textiles. Wastes from the electronics and rough pasture used for hill sheep farming, to industry cause heavy metal pollution at some sites arable regions in the lowlands where cereal crops especially Selkirk and Galashiels. Changes in metal are grown. The population is about 100,000 and discharges have occurred over li me as a result of industry is limited to a few small towns such as changes in legislation, improved facilities (either at Hawick, Galashiels, Selkirk and R dburgh. The the sewage treatment works or as part of industrial Tweed and its tributaries are clean and unpolluted processing) and a changing industrial base. An with only minor stretches below Class 1 status. example is Selkirk where copper and chromium Eutrophication can ticcur in some small lowland have declined whilst iron and lead have increased. watercourses, and diatom growth on the lower In sewage effl uent, organic chemicals, e.g. a moth- Tweed can be significant. Accidental pollution, proofi ng agent and some pesticide residues, have a often related to agricultural or industrial practices, mainly industrial source. Micro-organics in sewage occasionally causes fi sh kills. The Tweed river is a effl uent are site specific and, as with metals, there highly managed system and legislative and eco- have been changes over time for some species. nomic policies play an important role in determin- ing the water quality. Direct industrial discharges are very limited as a result of the Tweed RP1I's active policy of encour- Extensive water quality records have been col- aging, where possible, the connection of industrial lected by the Tweed River Purifi cation Board wastes to the local authority sewers. Landfill sites (Tweed RPM . Samples hum rivers and discharges have relatively little impact on water quality. Fish from sewage works, landfill sites and industry have farms cause depletion of dissolved oxygen levels been analysed for a wide range of determinands. and increases in suspended solids and total ammo- The report is based on data from 1985 to 1994. nia but these have little impact on water quality. Particular emphasis is placed on providing a regional perspective using a graphical approach. The results from the Tweed provide important The river water quality has been interpreted in background information against which better relation to catchment geography and to the ob- interpretation of more industrially based river served point source inputs to the catchment. systems can be made. This is important for issues such as the reduction of chemical loads to the For many determinands, both diffuse and point North Sea. The analysis of data sets such as these sources contribute to the overall riverine load, but provides important insights into the dominant to varying degrees. The importance of diffuse and factors affecting water quality and the relative point sources can be established by analysing the importance of point and diffuse inputs. Fo r ew o rd Since its formation in 1953 the Tweed River Purifi - record and relating this to the accumulated know l- catio n Board has achieved very signifi cant improve- edge of the Board's technical off icers has bee n a ments in the qua lity of the Tweed and its tributar- ma jor achieve ment and of credit to all concerned. ies, whilst always maintaining the focus on the Such is the advance in computing po wer, database changing demographical, agricultural, industrial development and software packages that the data and legislative pressures . At the present time 99.7% analysis within the report wo uld not have be en of the -rive rs within the Board's area are now of the possible even fi ve years ago. As a conse quence of highest quality (Class 1) with only minor stretches all this, the study provides the most comprehensive of fairly w ax] qua lity (Class 2); there are no rivers analysis of water quality of the Tweed ever unde r- of Class 3 or 4 qua lity. Th e Board's long standing taken. It endorses the mon itoring strategy of the cu lture has be en pollution prevention and a key Bo ard and strengthens the case for programmes eleme nt of its Mission Statement refers specifi cally such as 1.0 15. One of the purpose s of loo king at to prevention. The Board's strategy has been the Tweed was to examine a catchment which was largely based on the quantifi cation of po llution in relatively pristine condition and the influence of sources so that any improveme nts required have tho se issues which impinge upo n it - I be lieve the bee n on the basis of sound water quality and range of data presented , its background and its hydrological data derived from and supported by signifi cance, fully justifi es that purpose . Most its co mp rehe nsive samp ling, mo nitoring and importantly the repo rt points the way to future me asureme nt programme . monitoring and research goals which hopefully will stre ngt hen the link between the newly forming This report brings together the we alth of chemical, Environment Protect ion Age ncies and the Natural hyd rological and water manage me nt informatkm Environment Research Council. co llect ed by the Board . It prese nts the detailed scientifi c examination of that data within the co ntext of a major UK co mm un ity wide research J C Currie initiative , LOIS (Land Ocean Interaction Study). In Direct or and Rive r Ins p ecto r this resp ect, the process of examining such a major Tw eed River Pur ificatio n Boa rd F ro m c o v e r :p hotog raph sh ows the Tweed a bove Galaf oot (A .1 Robson) . Co n te n ts 1 I ntro d u ct io n 2 Backg ro u nd descrip tio n of tb e Tw eed ca tch m ent 3 2.1 Landscape, climate and population 2.2 General water quality 2.3 Inputs to the Tweed 3 Tb e da ta res o u rce 11 4 A g rap h ica l ap p roacb to reg ional da ta a na b,sis 15 4.1 Graphical presentation 4.2 Nitrate: a worked example 5 Water q u a lity in the Tw eed 23 5.1 Basic determinands 5.2 Metals 5.3 Micro-organic pollutant substances 6 I np u ts to tb e Tw eed 49 6.1 Summary of point source inputs 6.2 Summary of diffuse inputs 7 Tak ing tb ing s f u rth er 51 8 Conclu s io ns 55 A ck no w ledg em ents R ef erences Ap p end ic es Appendix A: tables of average concentrations Al Appendix B: detailed results for specifi c determinands Bl Appendix C: further regional analysis of nitrate Cl Appendix D: tables of sample site details á I I n tr o d u ctio n Th is re po rt describes the water q uality o f the UK rivers entering the North Sea .