Intensive Reconnaissance Sampling of Grand Canyon Tributaries, Grand Canyon National Park [Final Report]

Mazzu, Linda; Rihs, John

This report provides a summary of findings associated with the study entitled" Intensive Reconnaissance Sampling of Grand Canyon Tributaries" which was funded by the Water Resources division for FY 93 and FY 94. The objective of the study was to inventory water quality characteristics of as many Arizona state-protected waters as possible at locations of potential impact. With this information, a long term monitoring network of sites representing a diversity of watersheds and potential upstream impacts could be developed. Such a network will be recommended in this report. The main hypothesis discussed in the study plan was as follows: a subsample of water bodies selected to represent the diversity of watersheds draining into the Colorado River will be found to significantly differ in water quality composition by season, changing human use levels or discharge variations. The null hypothesis would be that water quality composition did not significantly differ. For this study, all tributaries were sampled at the mouth where heavy recreational use can occur and where any impacts from upstream could be identified. It is recognized that some tributaries require more than one sampling point depending on input locations. It is also recognized that some constituents found in small amounts at the mouth may be of much higher, and more problematic concentrations upstream or vice versa. This study is simply an attempt at identifying special properties, potential problems or constituents of concern that may warrant more intensive sampling along the length of the tributary. By addressing the hypothesis it can be determined if identified properties, problems or concerns are directly related to discharge, season or human use levels. And as mentioned above, this study has provided the opportunity to gather enough information to make sound recommendations as to the frequencies that tributaries should be sampled in the future based on these findings.