Estimation of Solute Fluxes from Ungaged Headwater Catchments in the Catskill Park of New York State

Predictions of flow and subsequent solute fluxes from ungaged basins have important implications both for water resources management and ecosystem monitoring studies. The Catskill region of New York State is one such place that requires both water resources management and ecosystem monitoring due to its strategic location as the main water-supplying region for New York City. This study examines the differences in chemical mass flux estimates made in ungaged basins using three different chemistry aggregation methods for solute concentrations determined from monthly grab samples. The efficacy of area ratios for predicting flow at the upstream location of a nested pair of stream gages based on flow at the downstream reference gage is also explored. The benefit of data set partitioning and development of separate prediction models for different flow regimes of the reference gage is analyzed, and a threshold of area ratio for use of such a method is established, with implications for use in ungaged basins. This work is focused on the Catskill region, but is likely to be applicable to other temperate, montane systems. Significant relationships were observed between upstream and downstream flow in all test watersheds. Furthermore, watershed area ratio was the most important basin parameter for estimating flow at the upstream location of a nested pair of stream gages. The area ratio alone explained 93% of the variance in the functional relation slopes that best fit the flow regressions. Data set partitioning was found to be beneficial only for nested pairs with area ratios greater than 0.1, and was determined by analysis of the root mean square error of the different flow prediction models. Five of the fifteen test watershed pairs had a lower root mean square error using the partitioned relationships and these pairs all had area ratios greater than 0.1. The relative difference between the three different chemistry aggregation methods was found to be relatively small on an annual basis (average difference of 7%) and increase with shorter time steps up to daily flux estimates (average difference of 26%). This finding indicates that simple flow estimation methods based on area ratios are justifiable, and perhaps preferred, for estimation of annual chemical mass fluxes, and that for such estimates of flux, the exact solute chemistry aggregation method matters little on an annual basis

Effects of Climate Nonstationarity on Low-Flow Models for Southern New England

Thesis advisor: Noah SnyderIncreasing attention has been drawn to the need for reliable streamflow estimates at ungaged locations under a range of climatic and hydrologic conditions. Climate projections for the northeastern United States over the 21st century--which include significant increases in temperature and precipitation--could have broad impacts on streamflows, potentially reducing the accuracies of existing streamflow models for the region. This thesis investigates recent changes in daily flow-durations in southern New England, and examines their influence on the reliability of the low-flow models for Massachusetts presented by Ries and Friesz (2000). An analysis of discharge data collected at gaging sites through water year 2012 revealed increases in nearly all flow durations at sites across southern New England since the mid-20th century, whereas very low flows (quantiles at or above the 95-percent exceedance probability) generally showed decreases, especially since the 1990s. Twenty-year moving streamflow quantiles at each of ten selected exceedance probabilities were examined for the periods of record of 16 streamflow-gaging stations in southern New England. The beginning of water year 1992 appeared to mark an inflection point in low-flow quantiles, before which very low flows were steady or increasing, and after which these flows showed near-universal decreases. While the observed peak in 20-year low-flow quantiles around 1992 may be due to the statistical method used to calculate the quantile trends, the inflection point could also be an indicator of when increasing evapotranspiration surpassed increasing precipitation as the principal climatic driver of changes in low flows in southern New England. The general upward translation of the flow-duration curve observed over the last 60 years is very likely linked to increases in annual precipitation during this period, while the decreases in very low flows are likely due to changes in climatic variables (increasing summer temperatures and evapotranspiration rates), and amplified by anthropogenic factors (greater areas of impervious surfaces and increasing rates of surface- and ground-water withdrawal). The data suggest that increasing precipitation rates have already caused the Ries and Friesz (2000) equations for the median low flows (Q50 to Q75) to become biased towards underestimation, and decreases in very low flows threaten to render the models for these flows biased towards overestimation in the coming decades. The streamflow quantile trends (for both the entire period of record of the gaging stations and just the post-1992 period) for each of the ten flow-durations of interest were extended into the future to the point where the corresponding Ries and Friesz (2000) model would fail (when actual flow durations would be outside the 90-percent prediction intervals for the estimated flows for greater than 10% of sites). The models for the lowest streamflows are estimated to lose validity by as early as 2018. Climate change is predicted to have significant effects on streamflow characteristics in southern New England over the 21st century, and the results of this study indicate that the Ries and Freisz (2000) low-flow models should be reformulated using more recent streamflow data within the next decade, and validated every 20 years thereafter to ensure their accuracies are maintained despite the effects of regional nonstationarity.Thesis (MS) — Boston College, 2014.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Earth and Environmental Sciences

Method for Estimating Low-flow Statistics for Ungaged Streams in the Lower Hudson River Basin, New York

Seven-day, 10-year and 7-day, 2-year low flow statistics were related to selected basin characteristics by multiple-regression analysis for 53 sites with watershed areas of less than 100 sq mi in the lower Hudson River basin. A common 20-year period of record was selected to ensure comparability of results. The most significant variable was the percentage of drainage basin underlain by stratified drift. The lowest standard errors of estimate were obtained from equations giving results in terms of discharge/sq mi during low-flow conditions. The statistically significant basin characteristics needed for estimating low flow were percentage of basin containing stratified drift, mean basin elevation, and mean annual precipitation. The smallest standard errors for 7-day, 10-year and 7-day, 2-year low flows obtained were 51% of the mean and 39% of the mean, respectively. (USGS

Towards a publicly available, map-based regional software tool to estimate unregulated daily streamflow at ungauged rivers

Streamflow information is critical for addressing any number of hydrologic problems. Often, streamflow information is needed at locations that are ungauged and, therefore, have no observations on which to base water management decisions. Furthermore, there has been increasing need for daily streamflow time series to manage rivers for both human and ecological functions. To facilitate negotiation between human and ecological demands for water, this paper presents the first publicly available, map-based, regional software tool to estimate historical, unregulated, daily streamflow time series (streamflow not affected by human alteration such as dams or water withdrawals) at any user-selected ungauged river location. The map interface allows users to locate and click on a river location, which then links to a spreadsheet-based program that computes estimates of daily streamflow for the river location selected. For a demonstration region in the northeast United States, daily streamflow was, in general, shown to be reliably estimated by the software tool. Estimating the highest and lowest streamflows that occurred in the demonstration region over the period from 1960 through 2004 also was accomplished but with more difficulty and limitations. The software tool provides a general framework that can be applied to other regions for which daily streamflow estimates are needed

Improved Methods and Guidelines for Modeling Stormwater Runoff from Surface Coal Mined Lands

The investgations, developments and guidelines for several hydrologic modeling strategies are presented. Investigations were conducted to determine appropriate event curve numbers for surface mined disturbed watersheds; and performance of four synthetic unit hydrograph models (SCS curvilinear, SCS single triangle, Williams and TVA double triangle) on 38 USDA experimental watersheds in 14 physiographic provinces using in excess of 270 events. A second test using only the SCS curvilinear unit hydrograph on 11 small watersheds and 48 events was conducted to investigate the excess rainfall pattern simulated with the curve number model. A procedure for developing a unit hydrograph using the time area method and a two parameter gamma distribution is presented for ungaged watersheds or watersheds undergoing land use changes. The development of a coupled explicit finite difference Green and Ampt infiltration-implicit finite element kinematic wave model is presented. The deterministic overland flow model includes a variable width which is essential for the accurate modeling of the watershed geometry. Both impervious and pervious watershed simulations are presented for the deterministic overland flow model

Analysis of streamflow variability in Oregon for regional water quality monitoring programs

Streamflow variability can provide valuable information for nonpoint source pollution monitoring program planning. The research papers presented in this thesis examine selected properties of streamflow variability in Oregon to advance its application in regional planning of water quality monitoring programs. The products of this research depict Oregon streams by their relative streamflow variability and evaluate factors that may influence that variability. The three manuscripts examine the application of streamflow variability in the context of regional strategic planning by addressing three related questions: 1.) What is the relationship in Oregon between streamflow variability and watershed size, which is often described as a proxy for streamflow variability?, 2.) What geographic factors in Oregon influence streamflow variability, and are regionalscale factors adequate to efficiently predict streamflow variability on ungaged streams?, and 3.) How is streamflow variability in Oregon affected by seasonal climatic variation? Examination of these questions regarding the behavior of streamflow variability of river systems in Oregon is used to assist in the design of regional and local water quality monitoring programs. Data are from historical records of established US Geological Survey gaging stations. Simple linear regression depicts the relationship of streamflow variability to basin size on a statewide basis and stratified by ecoregions. The results indicate that basin area is not an appropriate indicator of streamflow variability. Multiple regression is used to develop regional models of streamflow variability. Three models are developed for natural flow streams and streams with upstream diversions. Regional and watershed scale variables are evaluated for their potential contributions to the models. Watershed scale variables do not increase the predictive capacity of the models; therefore, the regional scale is appropriate for efficiently modeling streamflow variability. Seasonal investigation of streamflow variability in Oregon develops its application for seasonal monitoring programs. Spatial and temporal analysis reveal a weak relationship between annual and monthly streamflow variability, indicating potential for refined application of the variability index. Streamflow variability is an accessible tool for developing water quality monitoring programs. The regional scale distribution of streamflow variability in Oregon demonstrates the ease at which streamflow variability may be estimated on ungaged streams

Bankfull Hydraulic Geometry of Streams Draining the Southwestern Appalachians of Tennessee

The purpose of this study was to examine the bankfull recurrence interval for streams draining the Southwestern Appalachians Level III Ecoregion 68 of Tennessee, develop bankfull discharge and hydraulic geometry relationships for streams within the ecoregion and compare those relationships to the Ridge and Valley of Virginia, West Virginia, and Maryland (Keaton et al., 2005) and the Piedmont and Blue Ridge of North Carolina (Harman et al., 1999; Harman et al., 2000). For this investigation, a repeatable, systematic process was developed to locate bankfull stage within the Southwestern Appalachians during the spring and summer of 2005. The intent was to develop regional curves of empirically derived hydraulic relationships for this ecoregion, but first it was necessary to correctly identify bankfull stage in the sample streams. Bankfull discharge was defined as the effective discharge or channel-forming flow. Stream surveys were conducted on 11 study reaches (7 had USGS gages for calibration of bankfull) of various sized drainages across the ecoregion. Recurrence intervals were calculated using log Person Type III flood frequency analysis. Results demonstrated an average bankfull recurrence interval of 1.31 years for the Southwestern Appalachians, which was comparable to other nearby physiographic regions.Regional curves illustrate hydraulic and geomorphic relationships such as discharge versus watershed area, channel width versus channel cross sectional area and many more such relationships. The principal benefits from regional curves are their assistance in validating channel dimensions, pattern and profile for stream restoration designs. The marked variance in geology, climate, topography, and watershed land-uses across physiographic provinces drives the need for developing regional curves for each specific physiographic province. Stream restoration designs in Tennessee rely on curves from other nearby physiographic regions. A comparison of the Southwestern Appalachians regional curves developed in this study to the Ridge and Valley and the Piedmont and Blue Ridge reveals distinctly different relationships. In the Southwestern Appalachians, bankfull discharge and associated cross sectional area were found to be of much greater magnitude than streams in the other two regions