Thesis advisor: Noah P. Snyder / Estimating annual phosphorus (P) loading in impaired fresh water bodies is necessary to identify and prioritize management activities. A variety of monitoring programs and water quality models have been developed to estimate P loading in impaired watersheds. However, uncertainty associated with annual riverine P loads tends to receive less attention. This study addresses this gap by exploring the range in annual total phosphorus (TP) loads from two common load estimation methods using data collected in the Charles River watershed (CRW) in eastern Massachusetts. The CRW has two P Total Maximum Daily Load (TMDL) reports due to impairments with respect to excessive summer algal growth. Three estimation methods are used in this thesis to quantify annual TP loads (LY): the concentration-discharge relationship (CQ), the land use coefficient (LUC) method, and the average concentration, continuous discharge (ACQ) method. LY derived using the LUC method spanned an average relative percent range of 214% at each site, whereas LY results from the concentration-discharge method spanned an average relative percent range of 56%. While results of the CQ method produced a narrower range of LY, the CQ relationship is subject to seasonal dependencies and inconsistency through time. Seasonal terms in the LOADEST program, a publicly available and commonly used statistics tool, do allow the model estimates to capture trends through time, an advantage over the LUC method. Results of an interlaboratory comparison of P concentrations demonstrate the potentially large role of analytical uncertainty in LY estimation. Significant discrepancies between the results of each method for a single location and time suggest that loading estimates and consequently management priorities may be dependent on the estimation technique employed. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Thesis advisor: Noah Snyder / While it has been shown that extensive sedimentation in historic millponds has greatly affected streams in the Mid-Atlantic Piedmont region (Walter and Merritts, 2008), much less is known about the phenomenon in the heavily dammed areas of post-glacial New England. Some research has found similar deposits behind breached historic dams in the Sheepscot River watershed in mid-coast Maine, but at a smaller scale than those seen in the Mid-Atlantic region (Strouse, 2013; Hopkins, 2014). I attempt to further explore millpond sedimentation in New England by quantifying the volume of millpond sediment, also called legacy sediment, in the 171.3 km² upper Charles River watershed in eastern Massachusetts. Twenty three milldams were located in the watershed on 1850s maps, giving a damming density of 0.177 dams/km². Each historic dam that had since breached, 14 in total, was visited in the field to identify possible legacy sediment deposits. Legacy sediments were identified by their meter or higher terraces made of fine sands and silt and verified by comparison to sedimentary patterns found in other legacy sediment deposits and radiocarbon dating of material both within the legacy sediment and in the underlying layer. Legacy sediment terraces with an area of 1.68*10⁴ m² and a total volume of 1.29 - 2.57*10⁴ m³ were found upstream of two adjacent breached historic dam sites on the Charles River in Medway, MA. Radiocarbon dates from a coarse sand and gravel lower at 1.8 m depth returned pre-settlement dates of 1281-1391 cal AD (two σ). These dams were immediately downstream of a large glacial feature with steep banks along the river. The lack of legacy sediment at other dam sites and the lack of sedimentation behind intact dams suggest that a low sediment supply to millponds prevented legacy sediment deposits from forming in most of the watershed. / Thesis (BS) — Boston College, 2016. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.

Increasing suburban development has impaired water resources in the Charles River Watershed. Growing populations in the suburban fringes of Boston, Massachusetts have had a significant impact on ecosystems in the region. According to the EPA, one of the primary pollutants in the Charles River is phosphorus (EPA, 2010b). Phosphorus pollution contributes to algal blooms in the Charles that are harmful to ecosystems and toxic to humans (EPA, 2010b). In order to prevent existing suburban residential areas from contributing additional phosphorus to the Charles River, stormwater best management practices (BMPs) were studied to determine which BMPs effectively contain phosphorus. Infiltration trenches, bio-retention areas, and dry swales were selected and tested in scenarios developed for a neighborhood on Hartford Road in Bellingham, Massachusetts. The scenarios were intended to test a prioritized implementation strategy based on phosphorus loading hotspots and flow accumulation patterns. This study is intended to provide designers and planners a process through which site design can more effectively fit into broader ecological systems, specifically hydrological systems. The methodology developed in this study provides the ability to identify land cover types that contribute to phosphorus loading while also allowing phosphors loading hotspots to be identified at a scale as fine as 16 x 16 meters. Recognizing land cover types that contribute to phosphorus loading and prioritizing BMP implementation according to phosphorus loading hotspots within those land cover types allows for both economic BMP implementation efficiency and pollutant removal efficiency.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal