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Trends in total phosphorus and total nitrogen concentrations of tributaries to the Swan - Canning Estuary, 1987 to 1998

Hydrological Processes

By:
, , , , and
DOI: 10.1002/hyp.300

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Abstract

Temporal wet-season trends from 1987 to 1998 of total N and total P concentrations (TN and TP, respectively) in 14 tributaries to the Swan-Canning Estuary in Western Australia were evaluated using the Mann-Kendall or Seasonal kendall tests. Six of the catchments drained clay soils primarily on the Darling Plateau, which borders the sandy coastal plain on the east; two rural catchments drained the coastal plain; and six urban catchments drained the coastal plain. Generally, TN and TP were lower in tributaries draining clay soils than in tributaries draining siliceous sandy soils. Annual median TN and TP were relatively constant and no trends were detected in tributaries draining clay soils. TN and TP were higher (median TN = 1.6 and TP = 0.1 mg 1-1) and more variable temporally in tributaries draining the coastal plain. Statistically significant (?? < 0.01) TN trends were detected in 50% of the urban coastal plain tributaries and most were decreasing (-0.07 to +0.53 mg 1-1 year-1). Decreasing TP trends were detected at the two rural coastal plain tributaries and two of the urban drains (-0.01 to 0.15 mg 1-1 year-1 over periods from 5 to 12 years). Flow adjustment of TN and TP was responsible for removing trends in the raw data at some sites. The inter-annual variability of TN and TP of coastal plain tributaries was also related to the proximity of the water table to the land surface, which in turn was related to the annual precipitation. Fixed-interval sampling may be able to detect TN and TP changes associated with the implementation of management strategies in sandy coastal plain catchments. Tributary sampling during rainstorms and continuous monitoring of discharge are needed to better define processes controlling nutrient flux and concentration variability, and to detect trends in the urban catchments and the clay soil catchments, primarily those draining the Darling Plateau. Copyright ?? 2001 John Wiley and Sons, Ltd.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Trends in total phosphorus and total nitrogen concentrations of tributaries to the Swan - Canning Estuary, 1987 to 1998
Series title:
Hydrological Processes
DOI:
10.1002/hyp.300
Volume
15
Issue:
13
Year Published:
2001
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Hydrological Processes
First page:
2411
Last page:
2434
Number of Pages:
24