No abstract

The water-balance equation (equation 1) is solved for each month of the historical record in chronological order. The yield, Q y , is initially set equal to zero and is incrementally increased until the reservoir's usable storage is completely depleted during no more than one month of the simulation period. The resulting yield-the final value of Q y-is considered the firm yield of the reservoir. The firm yield calculated from the historical record does not include precipitation to or evaporation from the reservoir's surface. [Reservoir ID: identifier from figure 3. Altitudes are relative to NAD 83. AREA, reservoir drainage area plus surface area; PREC, average annual precipitation; SNOW, average annual snowfall; SOIL, maximum soil retention; B-ELEV, average drainage basin altitude; C-SLOPE, mean channel slope

1. This study evaluates the efficacy of remote sensing technology to monitor species composition, areal extent and density of aquatic plants (macrophytes and filamentous algae) in impoundments where their presence may violate water-quality standards. 2. Multispectral satellite (IKONOS) images and more than 500 in situ hyperspectral samples were acquired to map aquatic plant distributions. By analyzing field measurements, we created a library of hyperspectral signatures for a variety of aquatic plant species, associations and densities. We also used three vegetation indices. Normalized Difference Vegetation Index (NDVI), near-infrared (NIR)-Green Angle Index (NGAI) and normalized water absorption depth (D H ) , at wavelengths 554, 680, 820 and 977 nm to differentiate among aquatic plant species composition, areal density and thickness in cases where hyperspectral analysis yielded potentially ambiguous interpretations. 3. We compared the NDVI derived from IKONOS imagery with the in situ, hyperspectralderived NDVI. The IKONOS-based images were also compared to data obtained through routine visual observations. Our results confirmed that aquatic species composition alters spectral signatures and affects the accuracy of remote sensing of aquatic plant density. The results also demonstrated that the NGAI has apparent advantages in estimating density over the NDVI and the D H . 4. In the feature space of the three indices, 3D scatter plot analysis revealed that hyperspectral data can differentiate several aquatic plant associations. High-resolution multispectral imagery provided useful information to distinguish among biophysical aquatic plant characteristics. Classification analysis indicated that using satellite imagery to assess Lemna coverage yielded an overall agreement of 79% with visual observations and >90% agreement for the densest aquatic plant coverages. 5. Interpretation of biophysical parameters derived from high-resolution satellite or airborne imagery should prove to be a valuable approach for assessing the effectiveness of management practices for controlling aquatic plant growth in inland waters, as well as for routine monitoring of aquatic plants in lakes and suitable lentic environments.

Box plot showing rainfall-runoff coefficients for storms that occurred before (PRE) and after (POST) installation of low-impact-development (LID) features in the LID-retrofit neighborhood along Silver Lake Avenue and Dexter Street, Wilmington, MA. Rainfall-runoff coefficients are sorted by precipitation depth .

• Deicing of State and local roads was the largest source of sodium and chloride in the Scituate Reservoir drainage basin during Water Year (WY) 2000. Of approximately 1,000 tons of sodium and 2,300 tons of chloride introduced into the basin, 67 percent of the sodium and more than 90 percent of the chloride came from deicing of State highways, local roads, and other surfaces. Precipitation, individual sewage-disposal systems, and geologic weathering accounted for the remaining 33 percent of the sodium and 10 percent of the chloride inputs. The Scituate Reservoir system is the principal drinking-water supply for more than 60 percent of the population of Rhode Island. Sodium concentrations in the reservoir have been increasing slowly in recent years despite the long-term (12 years) use of a reduced-sodium deicing agent on State-maintained highways in the reservoir drainage basin. This report identifies the major sources of sodium and chloride in the drainage basin, and assesses the relative contribution of each source to the total amounts of these constituents that entered the basin from