Hydrogeological properties of the fine sand- coarse silt ('koppjord') in Solør, southeastem Norway

AJong Glåma in Solør the silty surface soil is named 'koppjord' and has been of great agricultural importance 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 obtained
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 300 mm per year during the period 1970-83. A certain groundwater recharge normally 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.