• Abstract and Figures
• Public Full-text

Hydrogeological properties of the fine sand- coarse silt ('koppjord') in Solør, _southeastem Norway SYLVI HALDORSEN, PETTER DEINBOLL JENSSEN & JOHN MARTIN SAMUELSEN Haldorsen, S., Jenssen, P. D. & Samuelsen, J. M.: Hydrogeological properties of the fine sand­ coarse silt ('koppjord') in Solør, southeastern Norway. Norsk Geologisk Tidsskrift, Vol. 66, pp. 223- 233. Oslo 1986. ISSN 0029-196X. AJong Glåma in Solør the silty surface soil is named 'koppjord' and has been of great agricultural im­ portance for many generations. At Haslemoen measurements of the saturated hydraulic conductivity in the field and in laboratory gave values between 4-10-6m/s and 5·10-5m/s, the highest values ob­ tained by field tests. Compared with other Norwegian Quaternary sediments the 'koppjord' has a very favourable pore system for plant-available water storage. A computer model shows that when the 'koppjord' is thicker than 0.5 m, there is no need for irrigation on cultivated land, even during dry summers. The average groundwater recharge estimate is 300mm per year during the period 197G--83. A certain groundwater recharge normal! y occurs even during the summer months. The infiltrability of the 'koppjord' is high enough to prevent surface ponding during snow melt and heavy autumn rain falls. S. Haldorsen, Department of geology, Agricultural University of Norway, P. O. Box 21, N-1432 Ås­ NLH, Norway. P. D. Jenssen & J. M. Samuelsen, Institute of Georesources and Pollution Research, P.O. Box 9, N- 1432 Ås-NLH, Norway. The surface soil along the river Glåma, between with a till overlain by clay and fine silt, which Kongsvinger and Våler in Solør, southeastern again was overlain by sand (Fig. 1). The fine­ Norway, is dominated by coarse silt and some grained surface sediment, covering the sand, the fine sand. The local name of this soil type is 'koppjord', was found to have a thickness of 'koppjord' (cup soil). The name indicates that 0. 5-1 m, but was in some places lacking in the frost upheaval makes the soil surface buckled, lower terraces along the river. This was later veri­ like upside-down plates. During many gener­ fied by Sortdal (1921). The fine-grained surface ations the soil has been known for its particularly sediment cover was interpreted by Bjørlykke large soil water storage capacity. This property (1901) and Sortdal (1921) as having been deposi­ makes it a very interesting soil type from both a ted in a lake extending from Kongsvinger to hydrogeological and an agricultural point of Våler. Holmsen (1954) pointed out that the sedi­ vie w. The soil has been mapped and de scribed in ments might have been deposited in more local several papers (i. e. Bjørlykke 1901, Sortdal 1921, ponds. A marine origin was supposed by Nielsen Holmsen 1954, Goffeng et aL 1980, 1981a, (1983) , while Høye & Sand (1983) found it more 1981b) , and it has been pointed out that the soil likely that the fine-grained cove r represented flu­ has much in common with the silt at Romerike, via! overbank deposits. southeast of Solør ('mjele') , and the silt in Øster­ The present study of the fine-grained surface dalen, north of Solør ('kvabb') (see e. g. sediments and hydrogeological aspects was car­ Bjørlykke 1901, Myhr 1980) . ried out at Haslemoen (Fig. 1) . The area studied The aim of this work has been to describe the consists of small terraces at different elevations hydrogeological characteristics of this special soil above the river Glåma's present channel (150 m type and the dependence upon sedimentological a. s. L ), and a greater terrace in the east at the properties. 172-175 m leve! (Fig. 2). In the northeast a higher terrace is found at 180 m. A fine-grained Description of the studied surface layer covers most terraces and there is an sediments abrupt boundary in grain size towards underlying coarser sand. The thickness of the fine-grained Bjørlykke (1901) described the sediments along surface sediments generally varies between O and Glåma in Solør and found a general stratigraphy 50 cm on low-lying terraces and 50-100 cm on the 16' 224 S. Haldorsen, P. D. Jenssen & J. M. Samuelsen NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Fig. l. Key map showing the main sediments along Glåma in Sediments along the river Glåma in Solør Solør in southeastern Norway. (After Sortdal 1921) Section through the sediments is shown in the lower left part. Studied area is framed. Simplified section across the main valley in Solør (Alter Bjørlykke 1901) 0 Coarse silt l fine sand ("Koppjord") D Sand § Clay l fine silt � Till "' km "' o 3 6 "' SOLØR NORSK GEOLOGISK TIDSSKRIFT 66 (1986) Hydrogeological properties 'koppjord', Solør 225 / �/� / � / Samptea ........ Terrace '-.. %@ � Channel D Peatland D BedrockO - 0.5m . 0.5- 1 m ;;; o 10 � >1m l"Koppj<><d" / km / Fig. 2. Map of Haslemoen showing the thickness of the 'koppjord' position of main terraces and drainage channels, samples and main field study localities. main terrace, while there are considerably sequence, on the contrary, indicates a sedimenta­ greater thicknesses at the highest terrace in the tion of mainly suspended material in quiet water. northeast (Fig. 2). In the areas where the surface layer is thinner The fine-grained sediment cover has a median than one metre, all the original sedimentary grain-size diameter varying between coarse silt structures are destroyed by weathering and frost and very fine sand, and it is moderately well to activity. It is, therefore, impossible to tell if the poorly sorted (Fig. 3). Due to soil weathering sedimentary structures described above are rep­ processes, the upper half metre has a significantly resentative for the fine-grained sediment cover in poorer sorting than in deeper parts of the sedi­ the entire area. River channels, which are fre­ ment. quent on terraces below 170 m a.s. l. , indicate The vertical variation was studied in more de­ that the surface sediments at the lower terraces tail at a locality in the northeast (site A, Fig. 2). consist of fluvial material, and may represent In this part of the area the thickness of the 'kopp­ overbank deposits. jord' is on the average more than two metres. A profile was excavated through a three metres thick section where 2.8 m coarse silt overlay a Saturated h draulic conductivit coarse sand. Underneath a 0.6 m thick zone dis­ y y turbed by cryoturbation, the sediments showed a Calculations of the saturated hydraulic conduct­ distinct planar lamination, with laminae of one to ivity were carried out from field and laboratory five centimetres thickness (Fig. 4). Each lamina tests and from the grain-size measurements at lo­ has a normal grading. By means of the grain-size cality A in the northeast (Fig. 2). analyses, the sequence can be divided into at The field measurements were made by a vari­ !east three different parts, each with an upward ant of the inverse auger hole method (Kessler & coarsening and each formed by several laminae Osterbaan 1974) described by Jenssen (1982). In sets. Longva (1984, 1986) interprets silt sedi­ this variant a constant head of water is used in the ments in the Romerike area and along the river pits and a porous plastic pad supports the pit Glåma as deposited during one flood event. This walls (Fig. SA). 226 S. Haldorsen, P. D. Jenssen & J. M. Samuelsen NORSK GE OLOGISK TIDSSKRIFf 66 (1986) The pits used were square, with a side length of Median diameter (Md) - sort ing (er;) 25 or 40 cm. Eleven pits were dug and the bot­ coarse silt - fine sand (•koppjord•) toms of the pits were approximately one metre 1.5 below the ground surface. The distance down to the groundwater leve! was more than four X X metres. o o The amount of water infiltrated per unit time � was measured at a water leve! of 20 cm. An al­ 1.0 +-::---+----------..-------� most constant infiltration rate (I) (steady state) � was reached after two-three hours, when the soil � �o o • around the infiltration pit was nearly saturated 2 (Fig. 5B). When assuming a constant head, a ver­ -ti=� :a.x.\ ., o Gl : •A • • •l tical one-dimensional flow and a hydraulic gra­ • • • � j: � · • 0.5 +-----;;--+---------_.!_: ---� dient equal to unity, the hydraulic conductivity ; . " can be calculated from the formula K=IIA where � � A is the total wetted wall and bottom area in the . � 0.2 - 0.4 m depth J !: x pit (Reynolds et al. 1983). These requirements i� • >0.4 m depth are never satisfied during a field infiltration test (e.g. Reynolds et al. 1985). However, a complete correction for three-dimensional flow around the Median diameter (Md) pit and the capillary suction requires more de­ Fig. 3. Median diameter (Md) - sorling (o1) diagram for 'kopp­ tailed measurements than carried out in this field jord' samples. Sorling coefficient after Folk & Ward (1957). test (see Jenssen 1986). The infiltration test is time consuming. lts advantage is that it gives average values for a greater sediment volume Sedimentology and hydrogeology of silt . than the other methods applied at Haslemoen, ( • kop p jord"), Haslemoen and that it also reflects the importance of macro­ .-=-.-------. - . - - --·r------.-c-:--:-:o------, :§ er, K(m/s) e structures like cracks and root channels. o 10-6 .c; Struc- (Folk & (Vol.%) 'Undisturbed' samples were taken by hammer­ c. tur es Md (�) Ward) (Hazen) une 1982 Q) o 0.5 1.0 2 4 6 20 40 ing steel cylinders of 5 cm diameter vertically and horizontally into the soil at different levels from O. 7 to 1.1 m below the ground. The hydraulic conductivity of these samples was measured by the constant head method ( description of the method is given in Jenssen (1982)).

Load more

  11

Copy Link