Sixty-six cross sections on the Colorado River downstream from the Paria and Little Colorado Rivers were monitored from June 1992 to February 1994 to provide data to evaluate the effect of releases from Glen Canyon Dam on channel sand storage and for development of multidimensional flow and sediment-transport models. Most of the network of monumented cross sections was established and first measured June-September 1992 and remeasured four times between then and January-February 1994. Each measurement consisted of 10 passes across the section, and data presented are the mean section and the standard deviation from the mean. Measured depths were converted to bed elevations using water-surface elevations measured or estimated for each reach. A line marked at regular intervals was strung across the river between the section end points and used to provide horizontal position control. A Wilcoxon rank-sum test was applied to the data, and bed-elevation differences between successive measurements that were statistically significant at the 5-percent significance level were identified and used to compute the difference in cross-sectional area from measurement to measurement. This report presents the data from the five measurements made during the reporting period in graphical form and describes the electronic form of the data. Bed-elevation differences and the computed/? value from the Wilcoxon rank-sum test are included in electronic form, and the format of the electronic files is described in the report.

Side canyons of Lake Powell are the most popular recreation areas of the Glen Canyon National Recreation Area in Arizona and Utah. There are more than 90 side canyons that are tributaries to the main lake body of Lake Powell. Near Bullfrog and Halls Crossing marinas in Utah, visitors frequent Knowles, Forgotten, and Moqui Canyons to fish, boat, camp, and hike the sandstone formations for which Lake Powell is famous. Areas of recreational activity are greatest near beaches in side canyons. Emissions from houseboats, personal watercraft, speedboats, and from some nonboating recreational activities introduce contaminants to the lake and to beach areas. The U.S. Geological Survey documented concentrations of trace elements, volatile organic compounds, organic wastewater contaminants, and other byproducts of fuel-based contaminants in water and bed material in Knowles, Forgotten, and Moqui Canyons during the summers of 2001 and 2002. Field work was conducted during four trips when recreational use was at a minimum (before Memorial Day in May) and when it was at a maximum (near Labor Day in September). Knowles Canyon was treated as a control; therefore, public access by motorcraft was not permitted during the study. Electric-powered or oar-powered research boats were used to collect samples and measure properties in Knowles Canyon. Record-low reservoir elevations during 2000-2002 limited the availability of camping and day-use beaches in Forgotten and Moqui Canyons. Although more beach areas were exposed during this period, the steep slopes of the beaches made it difficult to use the beaches for camping purposes. Side canyon waters of Knowles, Forgotten, and Moqui Canyons were similarly stratified (physically and chemically) during the study from natural advective and convective reservoir processes. Metalimnetic oxygen minimas were observed in September 2001 and 2002 in the side canyons and the main body of Lake Powell. Chemical concentrations of several organic constituents were elevated in Forgotten and Moqui Canyons during the high-use period in September of 2001 and 2002 compared with concentrations during the low-use period in May of 2001 and 2002. Concentrations of some constituents decreased from the mouth of each canyon to the canyon's headwaters, indicating that there could be a mechanism for constituent removal or that the main body of Lake Powell is not in equilibrium with the headwaters of the side canyons. Concentrations of volatile organic compounds, such as benzene, toluene, ethylbenzene, and xylene (BTEX compounds), were highest in the upper reaches of Forgotten and Moqui Canyons where visitor use was greatest. Trace amounts of some organic wastewater compounds, including cholesterol, N,N-diethyl-metatoluamide (DEET), and ethylenediaminetetraacetic acid (EDTA), were measured in Forgotten and Moqui 2 Effects of Recreational Use on Water Quality, Knowles, Forgotten, and Moqui Canyons, Lake Powell, Arizona and Utah Canyons. Except for minor concentrations of some volatile organic compounds and cholesterol,...