Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma

This data set consists of digital polygons of a constant
recharge rate for the alluvial and terrace deposits along the
Cimarron River from Freedom to Guthrie in northwestern
Oklahoma. Ground water in 1,305 square miles of Quaternary-age
alluvial and terrace deposits along the the Cimarron River from
Freedom to Guthrie is an important source of water for
irrigation, industrial, municipal, stock, and domestic
supplies. Alluvial and terrace deposits are composed of
interfingering lenses of clay, sandy clay, and cross-bedded
poorly sorted sand and gravel. The aquifer is composed of
hydraulically connected alluvial and terrace deposits that
unconformably overlie the Permian-age Formations.

A recharge value of 2.3 inches per year is used in this report
for the alluvial and terrace deposits along the the Cimarron
River from Freedom to Guthrie Oklahoma. The recharge rate was
estimated using a base-flow method and verified in a
steady-state flow model.

The polygon boundaries and the value for constant recharge for
alluvial and terrace deposits used in this data set were
published in a steady-state ground-water flow modeling report.
The aquifer boundaries along geological contacts were extracted
from published digital geology data sets. Additional boundaries
defining the geographic limits of the aquifer and areas of less
than 5 feet saturated thickness were digitized from a mylar map,
at a scale of 1:250,000. The maps were published at a scale of
1:900,000.

Ground-water flow models are numerical representations that
simplify and aggregate natural systems. Models are not unique;
different combinations of aquifer characteristics may produce
similar results. Therefore, values of recharge used in the
model and presented in this data set are not precise, but are
within a reasonable range when compared to independently
collected data.

本数据集包含美国俄克拉荷马州西北部锡马龙河（Cimarron River）从弗里敦（Freedom）至加斯里（Guthrie）沿线冲积层与阶地沉积物的恒定补给率数字多边形。该区域内面积达1305平方英里的第四纪冲积层与阶地沉积物中的地下水，是灌溉、工业、市政、畜牧及生活供水的重要水源。冲积层与阶地沉积物由互相穿插的黏土、砂质黏土透镜体，以及具交错层理、分选较差的砂与砾石组成。该含水层（aquifer）由水力连通的冲积层与阶地沉积物构成，以不整合接触关系覆于二叠纪地层之上。

本报告针对俄克拉荷马州锡马龙河弗里敦至加斯里段的冲积层与阶地沉积物，采用了2.3英寸/年的补给量数值。该补给率通过基流法估算，并经稳态流模型验证。

本数据集所用的多边形边界与冲积层、阶地沉积物恒定补给率数值，已发表于一篇稳态地下水流模拟报告中。沿地质接触带的含水层边界源自已公开的数字地质数据集。其余用于界定含水层地理范围及饱和厚度小于5英尺区域的边界，则从比例尺为1:250000的聚酯薄膜（Mylar）地图数字化而来，该类地图原始出版比例尺为1:900000。

地下水流模型是对自然系统进行简化与聚合的数值表征方法。模型并非唯一解：含水层特征的不同组合可得出相似的模拟结果。因此，本模型所用及本数据集呈现的补给率数值并非精确值，但相较于独立采集的实测数据，其处于合理区间范围内。