Gove, Nancy. 2001. Detecting relationships between land use and water quality trends: Questions of association, scale, and independence. Ph.D.
Human land use is one of the major factors affecting water quality. A
suite of water quality parameters, including nutrients and measures of
sediment, were sampled in one kilometer intervals on Willapa River, Mill
Creek and North River. A longitudinal profile of each water quality parameter
was used, providing much more information than a single observation. The
degree of connectivity from site to site and the effect of land use on
water quality depended on which water quality parameter was measured.
The predominant
land use and the observed relationships between water quality and land
use changed as different scales were used. The proximity of sampling locations
and the downstream flow of rivers causes independence to be an issue,
often resulting in underestimation of the variance of statistics used.
Understanding the effect of land use on water quality is a complicated
process requiring a thoughtful analysis to uncover all aspect of the relationship.