DWR_3555889 - Laserfiche WebLink

Rule 8.C.4) was added in response to the suggestion that the State Engineer should clarify the date to be used in determining the thickness of saturated aquifer materials for wells meeting the requirements of Section 37-90-137(5) , C.R.S. Rule 8.C.5) was added in response to the comments of numerous parties that wells that meet the exemptions set forth in Section 37-92-602(1 ) , C.R.S. should not be assigned cylinders of appropriation. Several parties presented testimony, concerning the de minimus effects of "exempt wells. " The Mat e Engineer agreed that, in7 light of both the testimony and the General Assembly's, intent in enacting Section 37-92-602, C.R.S. the cylinders of appropriation for exempt wells should not be considered and incorporated the language proposed by the City of Arvada, et al . Rule 8.D. identifies how the specific yield for the portion of the aquifer from which the permitted well will withdraw water is to be determined. This rule will standardize the: method used to determine specific yield. Since the specific yield determines how much water may be produced from a certain portion of saturated aquifer material, an accurate determination of specific yield is necessary in order for the State Engineer to calculate the allowed average annual amount of withdrawal . The specific yield to be used in calculating the allowable average annual amount of withdrawal should be spatially averaged over both the vertical and horizontal dimensions and be a weighted average for the claimed saturated aquifer materials oeneath the overlying land. Specific= yield values will vary depending on parameters such as grain size distribution, cementation, compaction, solution channel size, and fracture dimensions. --The---app-ropy-i-&te- -value for the specific yieldis the value that, when multiplied by the claimed saturated aquifer material thicKness and area of the property, will accurately reflect the amount of water to be drained by gravity from the aquifer beneath the overlying lancet Gravity is the force that causes water to enter the well and, thus, drain the aquifer. There are forces in the aquifer materials which will be acting against gravity to retain water in the aquifer. The amount of water which will drain from an aquifer is a function of how far the water table has been lowered and how long drainage is allowed to occur. For the de-termi nation of specific yield in these rules and regulations, it is assumed that the amount of water to be drained by gravity is not constrained by time, i .e. , for a s,pecific water level aecline all the.. . water will drain from, the aquifer within one hundred years. This assumption will result in a slightly larger value of specific y"I"J-d'�'a'an what may actually be reflected in nature.