During the summer of 1989, a water balance study was conducted at Lee Valley Reservoir, located approximately 19 miles southwest of the town of Eagar in Apache County, Arizona. The objectives of this study were to quantify evaporation and seepage losses from the lake and substantiate the use of a land-based evaporation pan to estimate lake evaporation. Lake level, inflow, controlled releases, precipitation and evaporation were measured on a twice weekly basis for six months from May 1 to October 31. Evaporation was measured in a Class A evaporation pan designed to float in the reservoir. Evaporation was also measured at a Class A land pan near the town of Eagar. A 1.0 inch difference in the estimated rate and the measured rate for a 147-day period of common record represents a 3.6% error between the land-based pan and the floating pan. Total losses from the lake over the six -month period were 224 acre-feet. Of this loss controlled releases accounted for 8.2 acre-feet, and evaporation was measured at 116 acre-feet. The remaining loss of 100 acre-feet is due to seepage, much of which can be seen as seeps rising within 800 feet downstream from the dam. Using average data from past years, an annual water balance for the lake was also calculated.

Although riparian system researchers intuitively understand the general role of flooding in these plant communities, very little quantitative analysis or physical modelling of these flooding effects has been undertaken. This paper describes a methodology for analyzing flood influences by utilizing vegetation monitoring along river transects and a sophisticated flood hydraulics computer model (HEC 2). The project is addressing important questions such as "What magnitude of foods will alter the physical structure and species composition of the plant community? Are major floods essential in creating open floodplain areas wherein regeneration of riparian plants can take place? How does flood timing during the growing season affect the germination of seeds and survival of seedlings?" The flood hydraulics study described herein provides an analysis method that is readily transferrable to other riparian systems, and anticipated results may offer some quantification of flooding characteristics which translate to any system composed of similar plant species. For instance. if mortality thresholds of such physical forces as flow velocity. depth. tractive shear stress, and stream power can be identified for selected riparian species, such information may be quite valuable to those engaged in restoration of disturbed systems. in specifying reservoir releases needed to maintain riparian vegetation downstream of dams, and in instream flow protection efforts seeking to protect essential environmental processes which sustain natural riparian systems.

A test protocol was evaluated for estimating the acute toxicity of urban stormwater runoff to aquatic life. Potential deleterious effects of storm flows on the aquatic community of small artificial impoundments were examined by application of short-term bioassays. Definitive, static renewal, acute toxicity tests were performed using the fathead minnow, Pimephales promelas, and the crustacean, Daphnia magna. The feasibility study indicated that short-term bioassays may provide an alternative to individual chemical constituent measurements and comparisons to numerical water quality criteria for protection of aquatic life. Biotoxicity tests may identify synergistic interactions to chemicals which individually meet specific water quality criteria but collectively lead to toxicity.

A study of over 11,000 event rainfall and associated direct runoff events from 100 small watersheds was done, in a search for distinct patterns of runoff response and/or association with land type. The results show unexpected variety in the geometry and scale of the rainfall -runoff response. Groupings of similar response type and magnitude were made, and the associations with vegetative cover were tested. Five separate response groups were identified as follows: 1) Inactive, characterized by no recorded responses to any rainstorm in an extended period of record; 2) Complacent, characterized by a very small part of the rainfall (ca 0.1 to 3 percent) being converted to direct runoff, often as a linear response; 3) Standard behavior, the expected "textbook" response common to agricultural lands and humid sites, and in which the runoff slope increases with increasing rainfall, and the scale of runoff far exceeds the complacent response; 4) Violent behavior, in which an abstraction threshold of 2 -6 cm clearly precedes a sudden high response; and 5) Abrupt response in which a very high portion of the rainfall is converted to event runoff without appreciable abstraction, as typified by extensively urbanized drainages. The responses and the group identifications were parameterized by a simple broken -line linear rainfall-runoff equation, and a dichotomous key based on coefficient values is proposed. Only mild associations between response type or coefficient values and the four vegetative covers (Forest, Range, Agriculture, and Urban) were found. The variety of hydrologic behavior on forested watersheds encompassed that of the other three land types.

New regulations concerning the management of underground storage tanks (USTs) have resulted in increased awareness of environmental contamination resulting from leaking USTs. The objective of the typical underground storage tank investigation is to determine if any subsurface contamination has occurred as a result of tank or product line leakage, fuel spills or overfills. Soil contamination at underground storage tank sites is usually discovered during the removal and replacement of USTs. Techniques that can be used to detect the presence of soil contamination adjacent to existing USTs include soil vapor analysis, exploratory boring, and soil and ground water sampling. The lateral and vertical extent of contamination must be determined at any site which contains detectable quantities of contamination. Two common methods for determining the extent of contamination are over-excavation and borehole drilling and sampling. Boring design and location considerations include number of borings, borehole depth and spacing, and site sub -surface conditions. Differentiation between perched sub -surface water and aquifers is critical. Once an appropriate boring plan has been established, then a sampling and analysis plan must be adopted that meets the needs of the particular investigation. The determination of the extent of contamination at an underground storage tank site is the first step leading to site closure and remediation.