Seepage loss-gain data were collected along four creeks (Leap, South Ash, Wet Sandy, and Leeds) that drain the eastern flank of the Pine Valley Mountains in southwestern Utah. Streamflow was measured at a minimum of eight sites on each of the four creeks during each of three (four on South Ash) seepage investigations at higher streamflows in May and June, and at lower streamflows during August, October, and November 1998. Only two reaches on Leap and Leeds Creeks showed a significant reversal of loss or gain trends between high and low streamflow where the difference in streamflow exceeded the measurement error.
Error analyses were computed both for individual reaches between consecutive measurement sites and for composite reaches between specified, nonconsecutive measurement sites to determine if seepage losses or gains exceed the error associated with measurement of streamflow. Computed losses or gains at 31 individual reaches exceed the normalized measurement error; 16 were along channel reaches that traverse unconsolidated deposits, 7 were associated with reaches that traverse sedimentary rocks other than Navajo Sandstone, 6 were associated with reaches that traverse the Navajo Sandstone, and 2 were associated with reaches that traverse rocks of igneous origin.
Composite reaches that encompass the outcrop of one of four hydrogeologic units (Navajo Sandstone, unconsolidated deposits, igneous rocks, or sedimentary rocks other than Navajo Sandstone) were used to compute the loss or gain based on the amount measured at the upstream and downstream nonconsecutive sites. For composite reaches that traverse outcrops of Navajo Sandstone, less water was measured at (or near) the downstream contact than at (or near) the upstream contact for 11 of the 13 seepage investigations. Of those 11 investigations with computed losses, the normalized difference (N d) was greater than the normalized error (Ne) for 6 investigations and confirms that a source of recharge to the Navajo Sandstone is seepage loss from the measured streams.
