Groundwater Contribution to a Mountain Stream Channel, Hedmark
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Groundwater contribution to a mountain stream channel , Hedmark, Norway. SYLVI HALDORSEN, JENS-OLAF ENGLUND, PER J0RGENSEN, LARS A. KIRKHUSMO & DAG HONGVE Haldorsen, S.. Englund, J-O., Jorgensen, P., Kirkhusmo, L.A. & Hongve, D. 1992: Groundwater contribution to a mounta in stream channel , Hedmark . Norway. Nor.geol.unders . 422.3-14. The Skvaldra stream in Hedmark, Southern Norway is characterized ~y a stable baseflow . This baseflow is controlled by a significant groundwater supp ly from Quaternary deposits. The area was chosen for an attempt at quant ification of the basenow's three groundwater components: (i) ground water from numerous springs on a sprinq-honzon at the boundary between permeable sediment-flow depos its in the upper valley side and compact basal till depos ited along the lower part of the valley sides and the valley bottom; (ii) groundwater from aquifers in compact basal till. topographically lower than the spring horizon; (iii) deep groun dw ater from till or underly ing bed rock . Flood events in the Skvaldra are due to surface run-o ff, usually confined to the valley bot tom along the stream channel , or due to very. shallow subsurface interflow , with very little or no groundwater compon ent. Even when the baseflow is very low « 0.05 rn's" ), groundwater from the springs makes up more than 70% of the total flow. Groundwater from the compact till constitutes about 10% of the baseflow, while deep gro undwater makes up less than 20%. During the summer the spring component is higher. During a year the baseflow varies between 0.03 and 0.1 rn's'", Most of this baseflow is due to groundwater, and the groundwater component is at least 1 x 10' m' per year, corres ponding to 10% of the annual precipitation . Sylvi rtetaorsen. Per Je rqensen, Jens-Olaf Englund, tnstitutt for jord fag, seksjon for geologi, Nor ges landbrukshogskole, Postboks 28, 1432 As, Norwa y. Lars A. Kirkhusm o, Norges geologiske underseke tse. Postboks 3813 - Ullev;jl Hageby, 0805-0510, Norway. Dag Hongve, Statens institutt for toncenetse, Geitmyrsveien 75, 0462 Oslo 4. Norway. Introduction in chemical and isotopic ratios of flow compo Terr ain covered by till or with a surface of nents. Observations from limnigrammes give strongly frost-weathered bedrock characteri some information about the hydrological pro zes the mountainous regions of south central perties of a catc hment. but these cannot be Norway. In some mountain a: eas the ground anything but qualified guesses wit hout field water contribution to streams and rivers is studies. Hewlett (1982) stated that «no graph i considerable. It gives a stable and significant calor mathematical operation performed on a baseflow and has an important influence upon hydrograph will reveal the sourc e or pathway the chemical composition of these waters. The of stormflow». Different comb inations of sour routing of water along surface and sub-s urfa ces and pathways can lead to quite similar ce flow paths in such mountainous areas is hydrographs. This study, therefore, uses che important because it influences the timing of mical data in addition to the volume, rate, and strea m flow and the chem ical composition of timing of streamflow to clarify the sources of water reaching the stream. In a catc hment ground water and the specific pathways along consisting of fractured bedrock over lain by which grou ndwater moves through a catch glacial sediments, the rivers may receive wa ment. ter from deep regional groundwater flow paths The Skvaldra catchment in Hedmark was as well as shallower water from the glacial selected for the study because the Skvaldra overbu rden. Two general approaches have stream receives groundwater from thick Qua been used to better define the sources and ternary depos its along the valley sides and actual flow paths of wate r in catchments (e.g. because human influence is small. It is therefo Horton 1933, Pinder & Jones 1969, Kirkby re well suited for an attempt to quantify the 1978, Germann 1986, Kennedy et al. 1986. different groundwater components which con Sklash et al. 1986); (i) physical observations tribute to the Skvaldra 's streamflo w. The inves fro m field stud ies, coupled with theoretical flow tigation is mainly based on data from the peri modelling. and (ii) measurements of changes od 1987 to 1991. 4 By/vi Ha/dorsen, Jens-Ote! Eng/und, Per Jerqensen, Lars A. Kirkhusmo & Dag Honqve NGU· BULL. 422. 1992 Study area coming from the east. In the western part of the catchment there are two small lakes (Fig. 1). The annual precipitat ion is about 1100 mm Topography, climate and land use (Fig. 2).Winters are norm ally cold with tempera tures well below aoe , and the snow falls from The study was car ried out in the uppe r part the beginn ing of November. The main sno w of the Skvaldra catc hment , Godlidalen, whi ch melt period is usua lly in the latter part of covers 13.5 km' (Fig. 1). Godlidalen is an asym May. Two of the study years, 1989 and 1990, metric valley with a rather flat valley floor, were exceptionally mild, with little or no snow bounded by mountainou s areas to the north accum ulation until late December and wit h the and east, and low er hills between the Skvald main snow melt in late April. ra catch ment and the main Astdalen valley to Peatland const itutes about 40 percent of the west. The altitude varies from 875 m abo Godlidalen, and dom inates completely below ve sea level (a.s.l.) in the valley bottom up to the timber line. The Skvaldra catc hment is 1090 m at the highest mountain summit in the used only for extensive graz ing by sheep, east. The Skvaldra stre am forms a dend ritic hunt ing and recreation. Other sources of pollu pattern , with most of the tributary streams ion are insignificant. Precipitation (mm) 70 60 '---'_---''----'3km 50 40 30 20 ' ~ . ., I " 10 . 00 . : • I ° • f ' .. 0 ~ ~ ! : :-~ ~ ~~ ~ - ~:. ~:- ~~~~ ~ _ h _ ~ ! , · : o • • •• • •-', . .. • ,_: ... • .:. ". : ;,:: i ;.. ;. .. JFMAMJ JASON D Discharge m 3s -' 20 - ...-/ Sk val d r a ca tchm ent Monitored pa rt of 15 · ca tchment area River o Gr ound w at er tu bewel l o Y Pre cipitation g auge ""'V Limnig raph Peat lands 5 Sprin g horizon Fig. 1. The Skvaldra catchment with position of the monito red part (Godlidalen). The profile a - a' is shown in Fig. 4. o J F D The western tube well is number 15006, the middle one 15007 and the eastern one 15008. Inset: 0 .d.= 0 sterdalen, Fig. 2. Precipitation at Sjusjeen 1990 and discharg e of the G.d.= Gudbra ndsdalen. Skvaldra in 1990. z - -<..------ 1 k m o C Dommant ground w a ter aJ oE- recharge ar ea ~ C r: Thin sacrments r c. and frost .. · Permeable weathered bedroc k !" -o· glacial seo tments '" -o· c I uva m a.s .t s ~· 1100 '" ~ 1050 Comp act basal (Ill 1000 Permeable and peat land sediments 9 50 900 "I--''-----LJ..........:,I!:l ""''' '-''-' c=. .,..J: ==c-=~-- _r. ---__,_- --,_--N..J 8 50 o 500 1000 1500 2000 2500 3000m ~=~ ~============= a a' l .-- -;r I : ,;;:/ 1 - 3· Bas e flow 4 Flood events '0 --- j~ 7 .r: Tate ru ngskampen " ==== peat Spri ng A unsaturated flow Spring s saturated flow -- - groundwater level springs Fig. 3. Depositional mode l for the Quatern ary sediments in Fig. 4. (a) W5W -ENE geo logical and hydrogeological pro file the Skva ldra catchment. a -a' through the southern par t of the Godlidalen based Top : Relation to the glac ier during glaciation. on the seismic investigations of Hillestad (1990). Position Bott om : Present day, show ing pos itio ns of the springs & of profi le is shown in Fig. 1. (b) Main hydrological budget peatland s. of the Skva ldra . 6 Sylvi Haldorsen , Jens-Olaf Englund. Per Jerqe rtsen, Lars A. Kirkhusmo & Dag Hongve NGU · BULL. 422. 1992 Bedro ck geology en clearly separ ated flood events, and it is The Skvaldra catchment is situated in the normally between 0.03"and 0.1 m's-I (Fig. 2). middle of a Late Precambrian sedimentary The annual baseflow is 1 - 3 x 10' m' , corre rock basin. The bedrock belongs to the upper sponding to 110 - 220 mm (Le. 10 - 20%) of part of the Brett urn form ation and consi sts the precipitation. During snowm elt floods , the of alternating fine-grained conglomerates and discharge in the Skvaldra can reach 20 m's-I. arkosic sandstones (Siedlecka et al. 1987). During the summer, stormflows of more than Seismic studies (Hillestad 1990) showed that 2 rn's' have been measured. the bedrock underlying the Quaterna ry sedi ments can be regarded as only moderately fractured,Le. with seismic velocities betwe en 4500 and 5500 ms-I. Monitoring The precipitation in summer was measured Quaternary geology with a Plumatic precipitation gauge (Fig. 1) The valley botto m and the lowest part of the and the data was proc essed by the Norwegian valley sides (about 6.5 km') are covered by a Meteorological Institute (DNMI Station 0676 compac t silty basal till of thick ness c. 10 m Astdalen - Skvaldra). During the winter, precipi (Kehler 1985, Hillestad 1990) (Figs. 3 & 4). Its tation data from the meteoro logical station at petrographic and granulometric composition Sjusjeen, 30 km west of Godlidalen, were is very homoge neous because it was formed used (DNMI Station 1296 Sjusjeen - Stora by comminution of the arkos ic bedrock alone sen). The precipitation data from Sjusjce n are (Haldorsen 1982, 1983).