Grid of streamflow variability index for Ohio

A generalized streamflow-variability index coverage was created by interpolating
a grid (with 6,066-ft^2 cells) from at-site values of the streamflow-variability
index computed for 133 rural, unregulated streamflow-gaging stations in Ohio and
nearby areas of adjacent states. Grid interpolation was done by means of the
interpolate surface routine contained in the Spatial Analyst extension of ArcView.
The inverse distance weighting (IDW) algorithm was used based on the 12 nearest
neighbors.

The streamflow-variability index at a streamflow-gaging station is defined as the
standard deviation of the logarithms of the 19 streamflow values at 5-percent
class intervals from 5 to 95 percent on the flow-duration curve (Searcy, 1959) of
daily mean streamflow for the analysis period.

Searcy, J.K., 1959, Flow-duration curves, manual of hydrology-part 2, low-flow
techniques: U.S. Geological Survey Water-Supply Paper 1542-A, 33 p.

本研究通过对俄亥俄州及邻省周边区域内133处乡村未受调节流量监测站计算得到的流量变异性指数（streamflow-variability index）实测值进行空间插值，生成了全域流量变异性指数栅格数据集，其栅格单元面积为6066平方英尺。栅格插值操作采用ArcView的空间分析（Spatial Analyst）扩展模块内置的表面插值工具完成，基于12个最近邻点调用反距离权重法（inverse distance weighting, IDW）算法进行计算。

单座流量监测站的流量变异性指数，定义为分析时段内日平均流量的流量历时曲线上，以5%为分级间隔、覆盖5%至95%区间的19组流量值的对数标准差（Searcy，1959）。

Searcy, J.K., 1959，流量历时曲线，《水文学手册第2部分：低流量技术》：美国地质调查局供水报告1542-A，共33页。