INTERA's Dr. Alaa Aly, P.E., Peter Castiglia, David Jordan, P.E., Patrick Tara, P.E., and David Lawler will speak on technical topics that include multivariate statistical methods for source water analysis, uncertainty analysis for hydrologic integration processes, bi-national groundwater resources, decision support systems, estimating un-gaged flows, and developing water resources with the Peace Corps. Additional details on their presentations are provided below. Dr. Alaa Aly, P.E., speaks on Multivariate Statistical Methods for Source Water Analysis and on Uncertainty analysis for Hydrologic Integration Processes at the American Water Resources Association's 43rd Annual Conference. Multivariate Statistical Methods: Multivariate statistical methods are used on water quality data collected from 34 vents at Silver Springs in Marion County, Florida. Strong spatial gradients and geochemical clusters are identified in waters entering Silver Springs. Three basic water types are identified that differ in their concentrations of sulfate, dissolved oxygen, Ca, Mg, alkalinity, Na, Cl and nitrate. One group of analytes associated with sulfate weathering and potential anthropogenic pollution or deep brines includes nitrate, sulfate, Na, Cl, and dissolved oxygen, and has strong north-south gradients and weak east-west gradients. Concentrations of these solutes are highest in the southern vents and decrease with distance north. A second group of solutes associated with carbonate weathering includes alkalinity (HCO3), Mg, Ca, and TDS and has strong east-west gradients with weak north-south gradients. Nitrate is correlated with Na and Cl, suggesting an anthropogenic source or deep brine high in NO3. The southern vents have the highest nitrate concentrations, suggesting they should be targeted for nitrate control. Future geochemical analysis using groundwater wells could identify the flow paths that contribute to the geochemistry of the springs and may suggest mitigation strategies for nitrate contamination. Hydrologic Integration Processes: MODBASINTM integrates the significant surface and subsurface hydrologic processes for the land based portion of the hydrologic cycle into a single software package. Through the coupling of surface water and ground water process models and the explicit representation of the vadose zone, MODBASIN provides a state-of-the-art public domain windows-based capability to simulate the interaction between surface water and ground water. MODBASIN uses physically-based delineations of land forms into land segments. Each land segment represents a homogeneous hydrologic response unit (HRU) within a drainage basin. A unique land segment is created by intersecting the drainage basins, land use, and soils coverage. MODBASIN parameters are directly derived from land cover and soil data. This paper focuses on the hydrologic integration processes as implemented in MODBASIN and explores the behavior of simulated evapotranspiration rates, groundwater recharge, and surface runoff and their relationships to the MODBASIN-controlling parameters. Utilized uncertainty characterization methods in this paper include Monte Carlo simulation (MCS) and first-order-second moment (FOSM) uncertainty analysis and propagation techniques, which cover the most common methods used for simple and complex models, respectively. Peter Castiglia speaks on Bi-national Groundwater Resources at the American Water Resources Association's 43rd Annual Conference. Bi-National Groundwater Resources: Transboundary aquifer systems along the U.S.-Mexico border pose challenges for inter-jurisdictional planning and water-resource management. Of the many groundwater basins in this region, the Palomas Basin system of the lower Mimbres Basin is unique. It is a regional sink for ground water, with an exceptionally large drainage area (~60,000 km2), and a history of climate events wet enough to establish large pluvial lakes in currently dry basins. The Palomas Basin system comprises a series of four interconnected sub-basins that discharge into shallow playa lakes (El Barreal, Laguna Guzman, Laguna El Fresnal, and Laguna Santa María) southwest of Ciudad Juarez. These groundwater basins (aquifer systems) provide water to communities in the border region. Recharge comes from precipitation within the Basin, which varies greatly with elevation. The high elevations of the Sierra Madre Occidental (above 3000 m) receive two to three times the annual precipitation of lower lying valleys to the east. In addition, predevelopment groundwater flow (1909) from the Mimbres Basin in southwestern New Mexico into the Palomas system provided additional recharge. However, as described in the Southwestern New Mexico Regional Water Plan, water use and water-level declines in the Deming and Columbus, New Mexico regions of the Mimbres Basin have affected these flow patterns. Conversely, little is known about water use on the Mexican side of the border and how water resources are being affected. This presentation summarizes the progress and challenges in characterizing the hydrogeologic framework of the Palomas Basin system along the New Mexico-Chihuahua border region, with an emphasis on work completed in Mexico. As one of several groundwater basins that provide water to communities along the border region, it is important that water managers understand the available resources as long-term water management plans are developed for the borderlands region. David Jordan, P.E., speaks on Decision Support Systems at the American Water Resources Association's 43rd Annual Conference. Decision Support Systems: INTERA worked with Santa Fe County, New Mexico, to develop a regional groundwater availability model and decision support system (DSS) to assist the County in evaluating potential well locations for groundwater supply sources to supplement surface water in a conjunctive use strategy. The groundwater availability model was used as part of a site suitability analysis DSS using multi-attribute utility theory (MAUT) to determine potential supply well locations. Using a geographic information systems (GIS) approach, the DSS identified potential supply well locations for the County that minimized impacts (and hence proximity) to existing supply wells, streams, and springs, while maximizing proximity to existing infrastructure, population centers, and areas of favorable geology and land ownership using a MAUT approach. As a final step, potential supply well locations were evaluated using the groundwater availability model to further refine the location alternatives to identify the most promising locations. This approach provided County decision-makers and the public with a structured, scientifically defensible, and unbiased method of identifying potential supply well locations. David Lawler speaks on Developing Water Resources with the Peace Corps at the American Water Resources Association's 43rd Annual Conference. Developing Water Resources with the Peace Corps: Year 2000 census data estimated the population of Honduras to be around 6.5 million people, 2 million of which lack access to basic water and sanitation services. These numbers are often poor estimates and the real number of people lacking access to clean water and sanitation is often much higher. Lack of access to potable water is considered the main factor in Honduras's high child mortality rate, about 59 out of 1000 births. The mission of Peace Corps' water and sanitation program is to help improve access to clean water and sanitation in rural areas. Currently 290 volunteers serve in 10 countries as water and sanitation engineers, specialists, and educators. During my two year service in Honduras I learned innumerable lessons about working with water resources in developing countries. One of the most important lessons was that developing a rural water resource is not a technical problem, it's a cultural one. If a community is not properly educated no technical solution will solve their water and sanitation problem. This was a hard lesson to learn, but it's one that I feel people who want to work in the water and sanitation sector need to understand. Peace Corps volunteers are uniquely positioned to assist outside organizations with their water and sanitation projects. All too often water projects fail soon after completion because the funding organization had little or no experience in organizing a community, building a water system, and educating its people on the operation and maintenance of that system. However, a Peace Corps volunteer can continually work in a community and devote themselves to the project for their entire two-year service, whereas most charities can only spend a week or two in country. By working through Peace Corps volunteers funding organizations can improve the sustainability of their projects and improve the effectiveness of their charitable giving. The developing world is full of water projects in need of funding and management. This is a perfect opportunity for people in the water resources industry to apply their knowledge and help improve the quality of life for people in developing countries like Honduras. Patrick Tara, P.E., speaks on Estimating Un-Gaged Flows at the American Water Resources Association's 43rd Annual Conference. Estimating Un-Gaged Flows: The Southwest Florida Water Management District of Florida is moving quickly on setting Minimum Flow and Levels (as required by Florida statutes) for priority water bodies. This work many times involves salinity analysis on estuaries in order to protect this vital resource. Obviously determining the freshwater inflows are an essential component of the overall process in protecting the estuarine environment. These freshwater inflows to the estuary are extremely difficult to measure due to the tidal influences and only recently has it even been possible. The historical flow gauges are located many miles inland to avoid the complications with the tides and in order to improve the stage/discharge rating. Therefore a large area of the contributing basin is un-gauged. Regression techniques can be applied to estimate these inflows assuming the land use conditions and other hydrologic factors remain consistent between the gauged and un-gauged portions of the basin. This assumption is seldom the case since there is a dramatic shift in the density of population and therefore development around the coast. HSPF has been applied to several basins in the District as a means to estimate the un-gauged flows. In these cases HSPF was calibrated using the observed flow data either within the basin or using a similar basin as a surrogate. The calibration must utilize the distribution of land use conditions in the model conceptualization in order to capture the dramatic change in basin characteristics and hydrologic response. The calibrated model parameters by land use can then be extrapolated to the un-gauged portion and used to predict the hydrologic response of the un-gauge sub-basins. This technique can also be utilized to extend the record of flow data when only a short period of observed data is available.