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N.E. Peters

Publications and source records attributed to N.E. Peters.

At least 19 recordsLinked to original sources
USGS2011

Water storage at the Panola Mountain Research Watershed, Georgia, USA

Storage is a major component of a catchment water balance particularly when the water balance components are evaluated on short time scales, that is, less than annual. We propose a method of determining the storage-discharge relation using an exponential function and daily precipitation, potential evapotranspiration (PET) and baseflow during the dormant season when evapotranspiration (ET) is low. The method was applied to the 22-year data series of the 0.41-ha forested Panola Mountain Research Watershed, Georgia. The relation of cumulative daily precipitation minus daily runoff and PET versus baseflow was highly significant (r2=0.92, p<0.0001), but the initial storage for each year varied markedly. For the 22-year study period, annual precipitation and runoff averaged 1240 and 380mm, respectively, whereas the absolute catchment storage range was ~400mm, averaging 219mm annually, which is attributed to contributions of soil water and groundwater. The soil moisture of a catchment average 1-m soil depth was evaluated and suggests that there was an active (changes in soil storage during stormflow) and passive (a longer-term seasonal cycle) soil water storage with ranges of 40-70 and 100-120mm, respectively. The active soil water storage was short term on the order of days during and immediately after rainstorms, and the passive or seasonal soil storage was highest during winter when ET was lowest and lowest during summer when ET was highest. An estimate of ET from daily changes in soil moisture (ETSM) during recessions was comparable with PET during the dormant season (1.5mmday-1) but was much lower during the growing season (June through August); monthly average SMET and PET ranged from 2.8 to 4.0mmday-1 and from 4.5 to 5.5mmday-1, respectively. The growing season difference is attributed to the overestimation of PET. ETSM estimates were comparable with those derived from hillslope water balances during sprinkling experiments. Master recession curves derived from the storage-discharge relation adjusted seasonally for ET (1.5 and 4.0mmday-1 during the dormant and growing seasons, respectively) fit actual recessions extremely well. ?? 2011 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS2011

Storage as a Metric of Catchment Comparison

The volume of water stored within a catchment, and its partitioning among groundwater, soil moisture, snowpack, vegetation, and surface water are the variables that ultimately characterize the state of the hydrologic system. Accordingly, storage may provide useful metrics for catchment comparison. Unfortunately, measuring and predicting the amount of water present in a catchment is seldom done; tracking the dynamics of these stores is even rarer. Storage moderates fluxes and exerts critical controls on a wide range of hydrologic and biologic functions of a catchment. While understanding runoff generation and other processes by which catchments release water will always be central to hydrologic science, it is equally essential to understand how catchments retain water. We have initiated a catchment comparison exercise to begin assessing the value of viewing catchments from the storage perspective. The exercise is based on existing data from five watersheds, no common experimental design, and no integrated modelling efforts. Rather, storage was estimated independently for each site. This briefing presents some initial results of the exercise, poses questions about the definitions and importance of storage and the storage perspective, and suggests future directions for ongoing activities.

Hydrological Processes↗
USGS2010

Gypsies in the palace: Experimentalist's view on the use of 3-D physics-based simulation of hillslope hydrological response

As a fundamental unit of the landscape, hillslopes are studied for their retention and release of water and nutrients across a wide range of ecosystems. The understanding of these near-surface processes is relevant to issues of runoff generation, groundwater-surface water interactions, catchment export of nutrients, dissolved organic carbon, contaminants (e.g. mercury) and ultimately surface water health. We develop a 3-D physics-based representation of the Panola Mountain Research Watershed experimental hillslope using the TOUGH2 sub-surface flow and transport simulator. A recent investigation of sub-surface flow within this experimental hillslope has generated important knowledge of threshold rainfall-runoff response and its relation to patterns of transient water table development. This work has identified components of the 3-D sub-surface, such as bedrock topography, that contribute to changing connectivity in saturated zones and the generation of sub-surface stormflow. Here, we test the ability of a 3-D hillslope model (both calibrated and uncalibrated) to simulate forested hillslope rainfall-runoff response and internal transient sub-surface stormflow dynamics. We also provide a transparent illustration of physics-based model development, issues of parameterization, examples of model rejection and usefulness of data types (e.g. runoff, mean soil moisture and transient water table depth) to the model enterprise. Our simulations show the inability of an uncalibrated model based on laboratory and field characterization of soil properties and topography to successfully simulate the integrated hydrological response or the distributed water table within the soil profile. Although not an uncommon result, the failure of the field-based characterized model to represent system behaviour is an important challenge that continues to vex scientists at many scales. We focus our attention particularly on examining the influence of bedrock permeability, soil anisotropy and drainable porosity on the development of patterns of transient groundwater and sub-surface flow. Internal dynamics of transient water table development prove to be essential in determining appropriate model parameterization. ?? 2010 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS2009

Effects of urbanization on stream water quality in the city of Atlanta, Georgia, USA

A long-term stream water quality monitoring network was established in the city of Atlanta, Georgia during 2003 to assess baseline water quality conditions and the effects of urbanization on stream water quality. Routine hydrologically based manual stream sampling, including several concurrent manual point and equal width increment sampling, was conducted ???12 times annually at 21 stations, with drainage areas ranging from 3.7 to 232 km 2 . Eleven of the stations are real-time (RT) stations having continuous measures of stream stage/ discharge, pH, dissolved oxygen, specific conductance, water temperature and turbidity, and automatic samplers for stormwater collection. Samples were analyzed for field parameters, and a broad suite of water quality and sediment-related constituents. Field parameters and concentrations of major ions, metals, nutrient species and coliform bacteria among stations were evaluated and with respect to watershed characteristics and plausible sources from 2003 through September 2007. Most constituent concentrations are much higher than nearby reference streams. Concentrations are statistically different among stations for several constituents, despite high variability both within and among stations. Routine manual sampling, automatic sampling during stormflows and RT water quality monitoring provided sufficient information about urban stream water quality variability to evaluate causes of water quality differences among streams. Fecal coliform bacteria concentrations of most samples exceeded Georgia's water quality standard for any water-usage class. High chloride concentrations occur at three stations and are hypothesized to be associated with discharges of chlorinated combined sewer overflows, drainage of swimming pool(s) and dissolution and transport during rainstorms of CaCl 2 , a deicing salt applied to roads during winter storms. One stream was affected by dissolution and transport of ammonium alum [NH 4 Al(SO 4 ) 2 ] from an alum-manufacturing plant; streamwater has low pH (<5), low alkalinity and high metals concentrations. Several trace metals exceed acute and chronic water quality standards and high concentrations are attributed to washoff from impervious surfaces.

Hydrological Processes↗
USGS2008

Consistency between hydrological models and field observations: Linking processes at the hillslope scale to hydrological responses at the watershed scale

The purpose of this paper is to identify simple connections between observations of hydrological processes at the hillslope scale and observations of the response of watersheds following rainfall, with a view to building a parsimonious model of catchment processes. The focus is on the well-studied Panola Mountain Research Watershed (PMRW), Georgia, USA. Recession analysis of discharge Q shows that while the relationship between dQ/dt and Q is approximately consistent with a linear reservoir for the hillslope, there is a deviation from linearity that becomes progressively larger with increasing spatial scale. To account for these scale differences conceptual models of streamflow recession are defined at both the hillslope scale and the watershed scale, and an assessment made as to whether models at the hillslope scale can be aggregated to be consistent with models at the watershed scale. Results from this study show that a model with parallel linear reservoirs provides the most plausible explanation (of those tested) for both the linear hillslope response to rainfall and non-linear recession behaviour observed at the watershed outlet. In this model each linear reservoir is associated with a landscape type. The parallel reservoir model is consistent with both geochemical analyses of hydrological flow paths and water balance estimates of bedrock recharge. Overall, this study demonstrates that standard approaches of using recession analysis to identify the functional form of storage-discharge relationships identify model structures that are inconsistent with field evidence, and that recession analysis at multiple spatial scales can provide useful insights into catchment behaviour. Copyright ?? 2008 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS2008

A reference data set of hillslope rainfall-runoff response, Panola Mountain Research Watershed, United States

Although many hillslope hydrologic investigations have been conducted in different climate, topographic, and geologic settings, subsurface stormflow remains a poorly characterized runoff process. Few, if any, of the existing data sets from these hillslope investigations are available for use by the scientific community for model development and validation or conceptualization of subsurface stormflow. We present a high-resolution spatial and temporal rainfall-runoff data set generated from the Panola Mountain Research Watershed trenched experimental hillslope. The data set includes surface and subsurface (bedrock surface) topographic information and time series of lateral subsurface flow at the trench, rainfall, and subsurface moisture content (distributed soil moisture content and groundwater levels) from January to June 2002. Copyright 2008 by the American Geophysical Union.

Water Resources Research↗
USGS2008

Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach

The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1 ng L −1 and MeHg was less than 0.2 ng L −1 . THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with POC at high flows, with maximum THg (MeHg) concentrations of 94 (2.56) ng L −1 at Sleepers River, Vermont; 112 (0.75) ng L −1 at Rio Icacos, Puerto Rico; and 55 (0.80) ng L −1 at Panola Mt., Georgia. Filtered (<0.7 μm) THg increased more modestly with flow in association with the hydrophobic acid fraction (HPOA) of DOC, with maximum filtered THg concentrations near 5 ng L −1 at both Sleepers and Icacos. At Andrews Creek, Colorado, THg export was also episodic but was dominated by filtered THg, as POC concentrations were low. MeHg typically tracked THg so that each site had a fairly constant MeHg/THg ratio, which ranged from near zero at Andrews to 15% at the low-relief, groundwater-dominated Allequash Creek, Wisconsin. Allequash was the only site with filtered MeHg consistently above detection, and the filtered fraction dominated both THg and MeHg. Relative to inputs in wet deposition, watershed retention of THg (minus any subsequent volatilization) was 96.6% at Allequash, 60% at Sleepers, and 83% at Andrews. Icacos had a net export of THg, possibly due to historic gold mining or frequent disturbance from landslides. Quantification and interpretation of Hg dynamics was facilitated by the small watershed approach with emphasis on event sampling.

Environmental Pollution↗
USGS2008

Water-quality monitoring and process understanding in support of environmental policy and management

The quantity and quality of freshwater at any point on the landscape reflect the combined effects of many processes operating along hydrological pathways within a drainage basin/watershed/catchment. Primary drivers for the availability of water are landscape changes and patterns, and the processes affecting the timing, magnitude, and intensity of precipitation, including global climate change. The degradation of air, land, and water in one part of a drainage basin can have negative effects on users downstream; the time and space scales of the effects are determined by the residence time along the various hydrological pathways. Hydrology affects transport, deposition, and recycling of inorganic materials and sediment. These components affect biota and associated ecosystem processes, which rely on sustainable flows throughout a drainage basin. Human activities on all spatial scales affect both water quantity and quality, and some human activities can have a disproportionate effect on an entire drainage basin. Aquatic systems have been continuously modified by agriculture, through land-use change, irrigation and navigation, disposal of urban, mining, and industrial wastes, and engineering modifications to the environment. Interdisciplinary integrated basin studies within the last several decades have provided a more comprehensive understanding of the linkages among air, land, and water resources. This understanding, coupled with environmental monitoring, has evolved a more multidisciplinary integrated approach to resource management, particularly within drainage basins.

Conference Paper↗
USGS2007

Responses of hydrochemical inorganic ions in the rainfall-runoff processes of the experimental catchments and its significance for tracing

Aimed at the rainfall-runoff tracing using inorganic ions, the experimental study is conducted in the Chuzhou Hydrology Laboratory with special designed experimental catchments, lysimeters, etc. The various runoff components including the surface runoff, interflow from the unsaturated zone and the groundwater flow from saturated zone were monitored hydrometrically. Hydrochemical inorganic ions including Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- + CO32-, NO3-, F-, NH4-, PO42-, SiO2 and, pH, EC, 18O were measured within a one month period for all processes of rainfall, various runoff components and groundwater within the catchment from 17 boreholes distributed in the Hydrohill Catchment, few soil water samples were also included. The results show that: (a) all the runoff components are distinctly identifiable from both the relationships of Ca2+ versus Cl-/SO42-, EC versus Na+/(Na+ + Ca2+) and, from most inorganic ions individually; (b) the variation of inorganic ions in surface runoff is the biggest than that in other flow components; (c) most ions has its lowermost concentration in rainfall process but it increases as the generation depths of runoff components increased; (d) quantitatively, ion processes of rainfall and groundwater flow display as two end members of that of other runoff components; and (e) the 18O processes of rainfall and runoff components show some correlation with that of inorganic ions. The results also show that the rainfall input is not always the main source of inorganic ions of various runoff outputs due to the process of infiltration and dissolution resulted from the pre-event processes. The amount and sources of Cl- of runoff components with various generation mechanisms challenge the current method of groundwater recharge estimation using Cl-.

Shuikexue Jinzhan/Advances in Water Science↗
USGS2006

Effect of bedrock permeability on subsurface stormflow and the water balance of a trenched hillslope at the Panola Mountain Research Watershed, Georgia, USA

The effect of bedrock permeability on subsurface stormflow initiation and the hillslope water balance is poorly understood. Previous hillslope hydrological studies at the Panola Mountain Research Watershed (PMRW), Georgia, USA, have assumed that the bedrock underlying the trenched hillslope is effectively impermeable. This paper presents a series of sprinkling experiments where we test the bedrock impermeability hypothesis at the PMRW. Specifically, we quantify the bedrock permeability effects on hillslope subsurface stormflow generation and the hillslope water balance at the PMRW. Five sprinkling experiments were performed by applying 882-1676 mm of rainfall over a ???5.5 m ?? 12 m area on the lower hillslope during ???8 days. In addition to water input and output captured at the trench, we measured transpiration in 14 trees on the slope to close the water balance. Of the 193 mm day-1 applied during the later part of the sprinkling experiments when soil moisture changes were small, < 14 mm day-1 was collected at the trench and <4 mm day-1 was transpired by the trees, with residual bedrock leakage of > 175 mm day-1 (91%). Bedrock moisture was measured at three locations downslope of the water collection system in the trench. Bedrock moisture responded quickly to precipitation in early spring. Peak tracer breakthrough in response to natural precipitation in the bedrock downslope from the trench was delayed only 2 days relative to peak tracer arrival in subsurface stormflow at the trench. Leakage to bedrock influences subsurface stormflow at the storm time-scale and also the water balance of the hillslope. This has important implications for the age and geochemistry of the water and thus how one models this hillslope and watershed. Copyright ?? 2006 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS2006

Water and solute mass balance of five small, relatively undisturbed watersheds in the U.S.

Geochemical mass balances were computed for water years 1992-1997 (October 1991 through September 1997) for the five watersheds of the U.S. Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) Program to determine the primary regional controls on yields of the major dissolved inorganic solutes. The sites, which vary markedly with respect to climate, geology, physiography, and ecology, are: Allequash Creek, Wisconsin (low-relief, humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Ri??o Icacos, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern hardwood forest). Streamwater output fluxes were determined by constructing empirical multivariate concentration models including discharge and seasonal components. Input fluxes were computed from weekly wet-only or bulk precipitation sampling. Despite uncertainties in input fluxes arising from poorly defined elevation gradients, lack of dry-deposition and occult-deposition measurements, and uncertain sea-salt contributions, the following was concluded: (1) for solutes derived primarily from rock weathering (Ca, Mg, Na, K, and H4SiO4), net fluxes (outputs in streamflow minus inputs in deposition) varied by two orders of magnitude, which is attributed to a large gradient in rock weathering rates controlled by climate and geologic parent material; (2) the net flux of atmospherically derived solutes (NH4, NO3, SO4, and Cl) was similar among sites, with SO4 being the most variable and NH4 and NO3 generally retained (except for NO 3 at Andrews); and (3) relations among monthly solute fluxes and differences among solute concentration model parameters yielded additional insights into comparative biogeochemical processes at the sites. ?? 2005 Elsevier B.V. All rights reserved.

Science of the Total Environment↗
USGS2003

Modelling hydrologic responses in a small forested catchment (Panola Mountain, Georgia, USA): A comparison of the original and a new dynamic TOPMODEL

Preliminary modelling results for a new version of the rainfall-runoff model TOPMODEL, dynamic TOPMODEL, are compared with those of the original TOPMODEL formulation for predicting streamflow at the Panola Mountain Research Watershed, Georgia. Dynamic TOPMODEL uses a kinematic wave routing of subsurface flow, which allows for dynamically variable upslope contributing areas, while retaining the concept of hydrological similarity to increase computational efficiency. Model performance in predicting discharge was assessed for the original TOPMODEL and for one landscape unit (LU) and three LU versions of the dynamic TOPMODEL (a bare rock area, hillslope with regolith <1 m, and a riparian zone with regolith ???5 m). All simulations used a 30 min time step for each of three water years. Each 1-LU model underpredicted the peak streamflow, and generally overpredicted recession streamflow during wet periods and underpredicted during dry periods. The difference between predicted recession streamflow generally was less for the dynamic TOPMODEL and smallest for the 3-LU model. Bayesian combination of results for different water years within the GLUE methodology left no behavioural original or 1-LU dynamic models and only 168 (of 96 000 sample parameter sets) for the 3-LU model. The efficiency for the streamflow prediction of the best 3-LU model was 0.83 for an individual year, but the results suggest that further improvements could be made. ?? 2003 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS2002

The role of bedrock topography on subsurface storm flow

We conducted a detailed study of subsurface flow and water table response coupled with digital terrain analysis (DTA) of surface and subsurface features at the hillslope scale in Panola Mountain Research Watershed (PMRW), Georgia. Subsurface storm flow contributions of macropore and matrix flow in different sections along an artificial trench face were highly variable in terms of timing, peak flow, recession characteristics, and total flow volume. The trench flow characteristics showed linkages with the spatial tensiometer response defining water table development upslope. DTA of the ground surface did not capture the observed spatial patterns of trench flow or tensiometric response. However, bedrock surface topographic indices significantly improved the estimation of spatial variation of flow at the trench. Point‐scale tensiometric data were also more highly correlated with the bedrock surface‐based indices. These relationships were further assessed for temporal changes throughout a rainstorm. Linkages between the bedrock indices and the trench flow and spatial water table responses improved during the wetter periods of the rainstorm, when the hillslope became more hydrologically connected. Our results clearly demonstrate that in developing a conceptual framework for understanding the mechanisms of runoff generation, local bedrock topography may be highly significant at the hillslope scale in some catchments where the bedrock surface acts as a relatively impermeable boundary.

Water Resources Research↗
USGS2002

Groundwater hydrochemistry in the active layer of the proglacial zone, Finsterwalderbreen, Svalbard

Glacial bulk meltwaters and active-layer groundwaters were sampled from the proglacial zone of Finsterwalderbreen during a single melt season in 1999, in order to determine the geochemical processes that maintain high chemical weathering rates in the proglacial zone of this glacier. Results demonstrate that the principle means of solute acquisition is the weathering of highly reactive moraine and fluvial active-layer sediments by supra-permafrost groundwaters. Active-layer groundwater derives from the thaw of the proglacial snowpack, buried ice and glacial bulk meltwaters. Groundwater evolves by sulphide oxidation and carbonate dissolution. Evaporation- and freeze-concentration of groundwater in summer and winter, respectively produce Mg-Ca-sulphate salts on the proglacial surface. Re-dissolution of these salts in early summer produces groundwaters that are supersaturated with respect to calcite. There is a pronounced spatial pattern to the geochemical evolution of groundwater. Close to the main proglacial channel, active layer sediments are flushed diurnally by bulk meltwaters. Here, Mg-Ca-sulphate deposits become exhausted in the early season and geochemical evolution proceeds by a combination of sulphide oxidation and carbonate dissolution. At greater distances from the channel, the dissolution of Mg-Ca-sulphate salts is a major influence and dilution by the bulk meltwaters is relatively minor. The influence of sulphate salt dissolution decreases during the sampling season, as these salts are exhausted and waters become increasingly routed by subsurface flowpaths. ?? 2002 Elsevier Science B.V. All rights reserved.

Journal of Hydrology↗
USGS2002

Status and trends in atmospheric deposition and emissions near Atlanta, Georgia, 1986-99

Wet and dry atmospheric deposition were investigated from weekly data, 1986-99 (1986-97 for dry deposition) at the Panola Mountain Research Watershed (PMRW), a forested research site 25 km, southeast of Atlanta, Georgia. Furthermore, the wet deposition was compared to that at three adjacent National Atmospheric Deposition Program's National Trends Network (NTN) sites (GA41, 50 km south of PMRW; AL99, 175 km northwest; NC25, 175 km north-northeast) and dry deposition was compared to that at adjacent Clean Air Status and Trends Network (CASTNET) sites, co-located at the NTN sites. The pH of precipitation is acidic and the dominant acid anion is SO 4 ; the pH (derived from the volume-weighted mean H concentration) averages 4.44 for 1986-99, and varies seasonally with average lowest values in summer (4.19) and highest in winter (4.63). From 1986-99, the annual wet deposition of sulfur (S) and nitrogen (N) averaged 400 and 300 eq ha -1 (6.4 and 4.2 kg ha -1 ), respectively. Inferential model estimates of annual dry S and N deposition from 1986-97 averaged 130 and 150 eq ha -1 (2.1 and 2.1 kg ha -1 ), respectively. From 1993-99, net S deposition (dry deposition plus canopy interactions) for coniferous and deciduous throughfall (throughfall minus wet-only deposition) averaged 400 and 150 eq ha-1 (6.4 and 2.1 kg ha-1), respectively. The annual wet deposition of S and N species at PMRW was comparable to that at NTN sites, with the exception of higher N species deposition at AL99 and relatively lower H, SO 4 and NO 3 deposition at GA41. Dry S deposition at PMRW differed markedly from the CASTNET sites despite similarity in S concentrations for all but NC25; the differences are attributed to differences in model parameters associated with the landscape and vegetation characteristics at the sites. At PMRW, atmospheric deposition trends were not detected for the entire sampling period, but were detected for shorter periods (4-5yr). Annual S and N deposition increased from 1986 to 1991, decreased to 1995 and then increased to 1999. SO 2 emissions from seven major point sources within 120 km of PMRW decreased markedly from the late 1980s to 1995 and have remained relatively constant or increased slightly from 1995 to 1998 Annual wet and dry S deposition at PMRW significantly correlates (p < 0.01) with SO2 emissions, and the correlation is dominated by the large SO 2 emissions decreases in the early 1990s, consistent with the implementation of Phase I of Title IV of the 1990 Clean Air Act Amendments.

Atmospheric Environment↗
USGS2001

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

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.

Hydrological Processes↗
USGS2001

Nutrient transport to the Swan - Canning Estuary, Western Australia

Catchment nutrient availability in Western Australia is primarily controlled by the disposal of animal waste and the type and rate of fertilizer application, particularly on the relatively narrow (~25 km wide), sandy coastal plain. Nitrogen (N) and phosphorous (P) concentrations and fluxes during the wet season of 15 tributaries, including four urban drains to the Swan-Canning Estuary, were evaluated from 1986 to 1992 and additionally concentrations only were evaluated throughout the year from 1993 to 1996. Concentrations of filtered reactive P (FRP) and total P (TP) were generally low, with the volume-weighted means for all sites being 0.06 mg 1-1 and 0.12 mg 1-1 respectively. The urban drains had higher TP concentrations (volume-weighted mean of 0.21 mg 1-1) than the streams (0.12 mg 1-1), with the high concentrations associated with particulate matter. Total inorganic N (TIN, NH4N plus NO3N) and total N (TN), which is of interest to eutrophic status of the N-limited estuary, were likewise low, compared with other developed areas having a similar climate. Both TIN and TN were higher in the urban drains (0.76 mg 1-1 and 1.5 mg 1-1 respectively) than the streams (0.31 mg 1-1 and 1.2 mg 1-1 respectively). The Avon River, which drains 98.5% of the 121 000 km2 catchment area, contributes most of the N (0.03 kg ha-1 year-1 or 65%) and a high percentage of the P (<0.01 kg ha-1 year-1 or 32%) to the estuaries. The Avon River nutrient fluxes are much less than other tributaries closer to the estuary. The coastal plain receives significantly higher rainfall (1,200 mm year-1) and has more intense horticulture and animal production than inland areas (<300 mm year-1). Annual rainfall is seasonal, occuring primarily from May through December. The surficial aquifers on the coastal plain generally are sandy with a low nutrient retention capacity, and rapidly transmit soluble and colloidal material in subsurface flow. Ellen Brook, on the coastal plain, drains pastures treated with superphosphate and has the highest FRP (0.51 mg 1-1), TP (0.7 mg 1-1) and TN (2.1 mg 1-1) of any tributary to the estuary. The coastal plain is also undergoing urbanization, particularly in areas adjacent to the estuary. Nutrients are subsequently available for transport during the onset of seasonal wet weather. Perennial baseflow from urban areas is an important source of nutrients. Water yield from the urban areas was high, being as much as 50% of annual rainfall. The timing of the nutrients delivered by the tributaries may be an important control on estuarine ecology. Copyright ?? 2001 John Wiley and Sons, Ltd.

Hydrological Processes↗