Blackie, J.R.

English

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•In s t itu te ofHyd r ologyNatu ral Env iro nme nt Re s e arc h Coun c il•44UPLAND AFFORESTAT ION ANDWATER RESCO RTE SIntertm S*port on tb eS alqUbite ezCa tulimem t S tudies 1S 81/ 82byJ 3t M a ckieInstitute of Hydrolog yIn troductionThe ob jective of this study w ithin the overall project is to compare thehydrological responses of a fores ted catchment w ith a comparab le non-forestedone  in a geographic and climatic situation typifying the areas of uplan dScotland where forestry and w ater resource interests may overlap . Of thevarious sites considered the K irkton and Monachyle Glens near Balquh idderappeared to offer the best comprom ise between climate , geography andvegetation on the one hand and access , amenable landowners and the feasilibityo f instrumen tation on the other . They also prov ided the op tion of ex tendingthe initial 5 yeir study to include the effects of forest planting on one andof progressive felling of m ature timber on the other .It w as recognised from the ou tset that instrumen tation of these catchmentsto provide data of the required standard m ay be feasible but wou ld certainlynot be easy . Year one of the project has proved the point . The summ ary of theyear 's work programm e on page 7 and the list of instrumentation installed inTable I give some indication of the prob lems encoun tered . M any have beenovercom e but oth ers are tak ing a little longer , and the cost will prob ablybe rather more than was estimated at this time last  year .  Nevertheless theIH team and the Work ing Group stand by the proposition that it is feasibleto instrum ent these catchmen ts and that the resu ltant data ob tained will beof an acceptab le standard .The Catchm en ts Figure 1 show s the location and re lative positions of the two catchm en ts .Wh ilst not imm ediate ly adjacent they are similar in size , aspect and altituderange . Geology and so ils are also similar , though there is an area ofrelatively flat deep peat in the upper b asin  of  the Monachyle which is absen tin the K irk ton . The Kirkton (Fig 2) covers app rox imately 685 ha of which275 ha is under mature plantations of sp ruce , larch and pine . The Monachyle(Fig 3) of 770 ha is under a vegetation cover sim ilar to that above the treeline in the Kirk ton , it comprises a mixture of upland grasses , heather andbracken . The grasses dom inant on the low er slopes , give w ay progress ivelyto heather as the altitude increases . There are considerab le areas ofex posed rock in both catchments .S I•aLaaT he ra in au e network and the weather stationsThe s torage raingauge netw orks we re des igned using dom ain theory w itha ltitu de , aspect and slope as the variables . The theory w as trans latedin to p ractical on-site locations in April and the first phase o fin stallation , using cross-coun try veh icle s , took p lace in M ay . TheAu tom atic Weather Stations in M on achy le an d on the Western rid ge of K irk tonw ere a lso insta lled during th is pe riod . In July a he licop ter w as usedto reach th e more in accessib le site s and the rem ain ing gauges in thefo rested area of the K irkton w ere installed .Ou tside the forested area all ra ingauges are in gr id-covered p itsw ith th eir funnels at ground le ve l and paralle l to the slope . W ith in thefo res t , specially mod ified 1 me tre high gauges are sited in su itab lesm a ll clear ings . The aerodynam ic e ffec ts wh ich cou ld resu lt in ser iousunderes tim ation of rain fall by such gauges in the open are considered tobe neg ligib le in these c learings . Some ju s tification fo r this has beenob tained from a com pariso n o f c atches w ith adjacen t ground level gau ges intw o c le arin gs , as shown in Figure 4 . Data from the recording rain gaugesattached to the weath er stations and from the add itional even t recorder inth e upp er M onachyle are used to dis trib ute in time the catches of them on th ly storage gau ges .The Au tom atic W eather Station in the M onachy le is a stan dard D id co tIn strum en ts type recording , a t 5 m inu te in terv als , so lar and ne t radiation ,tem perature , depression , w indspeed , w ind direction and rain fall onm agnetic tape . Tape and batterie s are ch anged at for tn igh tly intervals .In v iew of the poten tial difficu lties of access , the s tation on the wes ternr idge o f the K irkto n h as been set to record at 15 m inute in te rvals and b atte rypow er is ma in tained us ing a so lar p ane l . Th is station can operate unattendedfo r over two mon ths , though when conditions perm it the tap e is changedfortn igh tly .A ssessm en t o f snow in utW h ils t g round leve l g auges g ive the best m easure of liqu id precipitationin pu t , th ey are of little value when input is in the fo rm of drifting snow .Snow in pu t estim atio n presen ts particu lar difficu lties in this type of steepuneven te rrain . Further cons train ts arise in th is case from the difficu lty2of access in snow conditions and the presence of only one observer . Thefirs t winter had to be a period of experimen tation to assess the performanceand feasib ili ty of various techn iques .It was recogn ised that the best chance of actual snow fall measuremen twas in the sm all clearing sites in the forested area of K irk ton , wherelateral snow movemen t would be m inimised . Hence in these clearings the1 metre tall funne lled gauges mentioned above were designed to measuresnow as well as ra in inputs . As rainfall data accumulate it shou ld beposs ib le to determ ine the relationsh ips between the ground level gauges andthese clearing gauges . A first estimation of snow inpu t at all other sitescan then be ob tained by assum ing that the re lationships determ ined for rainfallare also applicab le to snow .Since it is not feasible to consider system atic depth/density snowcoursing after each snow even t, other approaches were considered . InN ovember sparse networks of snow po les were insta lled on a dom ain basiswith the design constrain t that they could be read , by tripod mountedtelescope , from a few key observation poin ts . The in tention was that these ,coupled w ith an altitude range of density m easurements , would give someestimate o f input for comparison w ith the ex trapolation from the forestgauges .A third approach adopted was to identify a few 'neutral ' sites inkey altitude/aspect dom ains and install snowmelt gauges at these . 'Neutral 'in this con text implies sites unlikely to be subject to excess accumulationor scouring of drifted snow . The melt gauge comprises a ground levelmounted gauge w ith the funnel covered w ith porous plastic grass . Threestorage and one recording version of these gauges were installed in eachcatchment in November/December .S tream flow measurementFrom the outset it w as recogn ised that the design and installation ofstructu res to give accu rate estim ates of stream flow from these catchmentswould presen t difficu lties . W ith the agreement of the Consortium theHydrau lics Research Station were comm issioned to design appropriate structures .Surveys of the re aches they suggested were carried out by Forth RiverPurification Board and drawn up by North of Scotland Hyd ro Board . An•assessment of the likely range of flows in each was carried out by IH .From this information HRS produced hydrau lic designs and recomm ended sitesfor them in June . Cons ideration of the engineering problems posed indicatedthat the HRS sites were not feasib le . Alternative sites were iden tified onwh ich the basic HRS designs cou ld be used and a full engineering drawingof the Kirkton structure was produced by SDD in September . ForestryComm ission undertook to build the structure , with IH supplying the steelcrests , and site preparation commenced in November . Severe conditions inDecember and  January  1982 delayed the work bu t completion of site preparationand construction is now sch eduled for as early as weather perm its in April 1982 .The Monachyle structure presents greater practical prob lems than theK irk ton one . Whilst an alternative  site  which w ill require less concrete thanthat proposed by HRS has been iden tified , there is an additional problem  inth at the present access track w ill not withstand the passage of the heavyplant and materia ls required for construction . The first kilometre inparticu lar is a priv ate farm track which w ou ld require major reconstructionto take the loads . Nego tiations to build an alternative access over the firstk ilom etre are proceeding w ith Forestry Comm ission . Assum ing that these aresuccessful a target of site preparation and construction in la te summer 1982should be feasible . Because of the delay Forth River Purification Boardagreed to install a temporary gauging station and cablew ay upstream of thestructu re site to provide som e initial estim ates of flow .Meteorolo ical  site  and  the  Third Weather StationThe agreed programme of instrumentation included the installation of am anually read meteo ro logical site to be supp lied by Meteorolog ical Officean d an adjacen t au tom atic weather s tation . These were to be sited at lowlevel in a position accessible under  all  conditions by the obse rver residen tin Tulloch Lodge , the objectives being to obtain base level data againstwh ich any gaps in the high level station records cou ld be infilled and toprovide a comparison of m anual and autom atic systems . The site originallyproposed proved to be fraugh t with local po litical difficulties and even tuallyhad to be abandoned .  Access  to an alternative s ite was negotiated andplanning permission for this site was received in February 1982 . Insta llationis now in hand .use of the combined gauges in the forest clearings to provide usable rainfalldata . Indirectly it also illustrates a prob lem du ring snow events . Whilstthe m ain reason for the discrepancy between the A31 ground level and combinedgauge du ring the snow period was an accumu lation of a snow drift over the groundlevel gau ge , part of it w as due to 'bridging ' of the combined gauge funneland partial loss of the snow built up on the bridge . This problem was observedto occur on several occasions . Redesign of the funnel rim of the gauge hasbeen done and a revised version is now on test alongside A3Y .A se ries of irritating teeth ing troub les with the Monachyle and KirktonWeather S tations , none of them re lated to site conditions , delayed the startof usab le data until August. Since then they have performed reasonab ly well ,though data were lost for part of January when it proved impossible to reach theMonachy le site to change tape and batteries . The Kirkton station appeared tosurvive th is period reasonab ly well ,  t h o u g h  the data suggest that icing may haveaffected some of the sensors intermittently . December and January temperaturesm ade it abundantly clear that the temperature range of the sensors will have tobe extended downw ards from the present - 15°C lim it .No u seful inform ation 'was ob tained from the snowpo les during the December/January snow even ts . Access to the selected observation sites immediately aftersom e snow fall events was not poss ible with the equipment required . On otheroccasions low cloud m ade it impossible to 'read ' the poles from the sites .C learly some re-thinking of the approach is required during the coming year .Lessons learned(1) Read ing the storage gauge network s , and the other instrum en tation at therequired in tervals is feasible w ith one observer during no-snow conditions .(2) In snow conditions an additional observer on site is essential to ob ta in ausefu l re tu rn on the investment in instrumentation . Work ing together theywou ld increase  t h e  effective rad ius of ope ration in the catchments and , whenconditions perm it them to work individually , they could increase the poss iblework load in the short periods of winter day light .4041Data Analysis and instrument assessment41In terms of the overall objectives of the project no mean ingful analysisis possib le yet on the sho rt runs of data accumulated . Nevertheless these datahave provided usefu l indications of instrument performance and suitability forthe job . Figure 4 , for example , provides some initial justification for the4041'1; 1(3) With increased experience the observer shou ld be able to make greater useof the ex isting IH cross country veh icle as a means of access .to the catchmen tsin deep snow conditions . A suitab le tracked vehicle could increase the limitsunder which access is possib le . W ithin the catchmen ts , skis are the onlypractical means of travel above the valley bottom in Mon achyle or above thetree-line in Kirkton . This limits the observer 's ab ility to carry batteriesor other equipment and is a constraint that must be borne in mind whenredesigning snow measurement techniques .(4) Solar cells and w ind generators to sustain battery power have provedpracticable in the environment of the catchments ; these , together with longduration logg ing equipmen t , should be used for w inter data co llection wheneverpossib le .1982/83 ProgrammeFollow ing the anticipated installation of the meteorolog ical site and thethird weather station in M arch the next priority for the coming year is theconstruction and instrum en tation of the Kirkton Weir in April.6Decisions on imp roving access to the Monachyle must be made in M arch if thatstructure is to be comple ted in the summer .Beyond that , a decision must  be  made on 'whether to proceed with the p roposedsecond stru cture in the Monachyle (Figure 3) and appropriate ac tion taken .During the summer the snow measuremen t system s must be modified to give abetter return of  data  consis tent with the difficu lties of access . W ith minormodificiations the combined clearing gauges in Kirkton have proved adequatebut the snow po le system must be modified . No judgement can be made onthe snowm elt system until the readings have been recovered and examined .W ith the completion of the streamflow structures accumulation of fu llhydrological data w ill begin .The reafter sed iment lo ads can also be measured using the structures asbedload traps . Ob servation suggests that suspended sediment loads are very lowbut a system atic sampling programme will be initiated fo llowing comple tion ofthe structures .JRB/JVPC atchmen t S tudies3981January - M archAprilM ayJune Structure designs received from HRS .JulyAugustSep temberOctoberDecem berFebruary1982Work programm esumm arySite investigations at Balquhidder .Access agreements w ith landowners .Surveys of streamflow structure sites .PR work w ith local residen ts .AGREEMENT TO PflOCEED ti TH BALQUNIDDER CATCHMENTS .Raingauge network design comp leted .Sites iden tified and flagged in catchm en ts .Sites for weather s tations iden tified .Tulloch Lodge made availab le to IH .Phase 1 of raingauge network installation .Kirkton and Monachyle AW S installed .Site meeting - Consortium working group .M r Johnson took up post as observer , based onTu lloch Lodge .Phase 2 of raing auge network installation .Site visits to ex am ine alternative structuresites on Kirkton and Monachyle .Surveys of alternative structure sites (FRP B) .Drawings of stru ctures prepared (SDD) .Rou tine rainfall and weather station datacollection initiated .Combined snow/rainfall gauges installed' in clearingsin Kirkton .Design of additional snow networks .Temporary gauging station installed in ,Monachy le(FRPB )Neutron probe networks under heather (Monachyle )and spruce (Kirk ton)November Installation of snow .poles and snowm elt gauges .Rock blasting at K irk ton structure site (FC ) .Installation of snow through fall gauges in Kirktonforest site .Planning applications subm itted for Met site andstreamflow structures .January Heavy dr ifting of snow created severe accessproblems for resident observer .W ind generator installed to power snowmelt gaugein Kirkton .Site meeting (SDD , IH , FC) to finalise constructionplans.for Kirk ton structure and to considerMonachyle site and access prob lems .M arch Third weather station and m an ual met, stationinstalled on Tu lloch farm site .414141414141•4 ,Instrumentation installed on the Balquh idder catchm ents .I ternAutomatic Weathe rS tations (incorporatingrecording raingauge)Ground level storage 6 (+ 3*)raingaugesRainfall event recordersCombined snow/rainfallTable IK IRKTON (Forested) MONACHYLE (Con trol)S to r a g e gaugesRecording snowm elt gaugesSnow poles 121 (Summ er 82)Streamflow structures 1 (Spring 82)In addition , one site under heather (Monachyle ) and 1 under spruce (Kirk ton)have been instrum en ted for so il moisture studies and a site under spruce(Kirk ton) has been instrtm en ted to measure snow throughfall .* These are located alongside 3 combined gauges for comparison purposes .t This is a Met Office MTER alongside the Weather Station .1 (Autumn 82. provisionally700 Boo 96(3800 700600500 400 300.2200990500Scale 1:50,000Con tours In met rosrm400300 300 400 500700600 Loal von f igure 1KIrkton Glen6005004008000600 200eoob 9ets te14.1 sisBALOUHIDDER CATCHMENTSBalquhR.Balvag300 A84 Stirring0 0• • • • • •70060 060 070 • ,\ ‘.\ \ A '‘ . .'. -N• \„ ‘‘\ ,\\\\\\„„S. f igure 2KIRKTON CATCHMENTI si n 6 .8 km2 1800•800••0` 40 0300,4150060080080060 080 01 kmGround level re ingauge •Snowmen gauge 0Record ing re inga uge •Automat ic weather stat ion •Neut ron probe site VProposed sit e tor seconds t re a rnf low st ru ct ureFo restry Commiss ion fe nceMONACHYLE CATCHM ENT I e fe a 7.7 km2 1frRe ........, ‘ 4. 4. _%• .I •I N %6 I I 1I/70 • oe4= 1 • • •500f ig u re 360 07..1700•300200anowgaugeI mm I1006 '6 6 • '6 '6 b • • • • •K IRKTON RAINGAUGE COMPARISON1 : 1 lino0groundlinel gaug• I mm I10 200f igure 40S115ASSitsA3YB 3W 0A3W X.5 indIcatn significantsnowfal l400ANaturalEnvironmentRese arc hCounc il

Upland afforestation and water resources - interim report on the Balquhidder Catchment Studies 1981/82

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Upland afforestation and water resources - interim report on the Balquhidder Catchment Studies 1981/82

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