Title: The Hydrography of Estuary, Delaware z the Murderkill
Abstract:The hydrography of the lower Murderkill River, a small, Shallow estuary in southeastern Delaware, was studied from July, 1967, through December, 1970. Variations of current velocity, tide stage, salin...The hydrography of the lower Murderkill River, a small, Shallow estuary in southeastern Delaware, was studied from July, 1967, through December, 1970. Variations of current velocity, tide stage, salinity, water temperature, and dissolved oxygen were measured at one station in the estuary during periods of mean and high freshwater runoff. The flushing time and mixing characteristics of the estuary during mean runoff were determined using a water-tracer dye. Seasonal and tidal variations of salinity, water temperature, dissolved oxygen, pH and turbidity were measured at seven stations along the estuary from September, 1969 through December, 1970. The Murderkill Estuary has characteristics of both a well-mixed and partiaUy-mixed estuary. The prevailing hydrographic regime is maintained by tidal mixing and forced river flow which disrupt density-induced, internal circulation. Approximately 90% of the upsffeam salt flux is maintained by diffusion. During mean freshwater runoff the estuary discharges 1.7 l0 s m 3 of freshwater seaward per tidal cycle and has a flushing time of 4.4 tidal cycles. The flushing time decreases from 18.4 tidal cycles during low runoff, 3.1 104 m 3 per tidal cycle, to 2.6 tidal cycles during high runoff, 3.1 l0 s m 3 per tidal cycle. The proposed daily discharge of 3.8 104 m 3 of sewage effluent into the estuary will shorten the flushing time of the estuary at the discharge site from 4.4 to 3.9 tidal cycles during mean runoff. Salinity distributions in the estuary are highly variable. At high water, the lower reaches of the estuary are occupied by moderately saline water, 15.7 to 28.2 o/oo, from lower Delaware Bay. Vertical and longitudinal salinity gradients are small. In the central section of the estuary, salinity decreases from values characteristic of lower Delaware Bay to 1.0 o/oo. Mean vertical salinity differences are 2.0 o/oo, and the mean longitudinal salinity gradient is 2.7 o/oo per km. In tidal freshwater, salinity does not exceed 1.0 o/oo, and salinity gradients, vertical and longitudinal, are small. At low water, salinity in the lower reaches of the estuary is reduced substantially. The water column is well mixed, and the mean longitudinal salinity gradient is 2.4 o/oo per km. Tidal freshwater occupies the upstream 30% to 70% of the estuary with increasing runoff. Dissolved oxygen concentrations in the estuary range from 10 to 12 rag/liter during the winter to 2 to 3 mg/liter during the summer. A zone of oxygen depletion appears in the central section of the estuary. This section will receive the effluent from the sewage-treatment facility. Oxygenated water presently enters the central section of the estuary from inland freshwater runoff and from lower Delaware Bay.Read More
Publication Year: 1974
Publication Date: 1974-01-01
Language: en
Type: article
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