Assessing Global River Water Quality - ACS Publications - American

Chapter 13

Assessing Global River Water Quality Case Study Using Mechanistic Approaches David A. Dunnette

Downloaded by FUDAN UNIV on March 3, 2017 | http://pubs.acs.org Publication Date: February 4, 1992 | doi: 10.1021/bk-1992-0483.ch013

Environmental Sciences and Resources Program, Portland State University, P.O. Box 751, Portland, OR 97207 Rivers, like the atmosphere and oceans, are integrative and reflect conditions within their boundaries. Critical to an understanding of the role of human activity in environmental change is an understanding of the impact of human activity on river quality and how river quality may be used as an indicator of environmental change. Current data collection practices, based largely on the traditional parametric or ambient fixed-station network approach, do not generally provide the information necessary to relate human activity to quality of river water or to utilize water quality data as an indicator of global environmental change. What is needed is an alternative approach which permits development of valid cause and effect relationships. This strategy, one involving intensive surveys, is referred to here as mechanistic. The Willamette River, Oregon, USA, is used as a case study to illustrate quantitative, semi-quantitative and qualitative approaches to mechanistic assessment of river water quality using, respectively, dissolved oxygen depletion, erosion/deposition and potentially toxic trace elements as examples. The Willamette River Basin, Oregon serves as an excellent case study of river quality assessment for a number of reasons. First, the Willamette River has been cited internationally as a classic example of how water quality can be restored from a previously poor quality waterway (1-3). Second, excellent background data were available, particularly on hydrology. Third, at the time most of these studies were initiated, the Willamette River was the largest river in the U.S. for which all point-source discharges were receiving secondary wastewater treatment. The Willamette River is the twelfth largest river in the U.S. and has been studied extensively for over sixty years. The early history of the river was

0097-6156/92/0483-0260$07.75/0 © 1992 American Chemical Society Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992.


13 DUNNETTE

Mechanistic Approaches to River Water Quality

261

characterized by low dissolved oxygen and high levels of fecal coliform bacteria due to discharges of untreated municipal wastes, pulp and paper effluents and vegetable processing wastes. Public concern over the river's condition quickened in the 1930s and following WWII construction of wastewater treatment plants began in earnest. By the 1960s, conditions in the river had improved to such an extent that for the first time in several decades, fall Chinook salmon returned to the lowerriverand its tributaries. The experience was one of the first to demonstrate that a major heavily polluted river could be restored to health (1). The goals of this chapter do not include a "state of the art" literature review which would be appropriate for a more in-depth discussion of one particular problem area. Rather the intent is to illustrate mechanistic approaches to river quality assessment using the three globally relevant water quality problem areas discussed in the previous chapter: dissolved oxygen depletion, erosion/deposition, and potentially toxic trace elements. The information provided does not include all rationale, methology or approaches used in the study as this is beyond the scope of the chapter. Additional general information on application of the intensive river quality assessment approach in the Willamette River basin may be found elsewhere (4-9, 11-14, 17). Physical Setting The Willamette River basin (Figure 1) contains Oregon's three largest cities (Portland, Eugene and Salem) and includes more than two-thirds of the states population within a drainage area of 30,000 km . About fifty percent of the land is forested. Agriculture is practiced intensively in the valley where irrigation is by sprinkler. The primary industries are pulp and paper, lumber, electronics, and tourism. The basin supports extensive wildlife and fish habitat. Precipitation varies from 100 cm at the basin floor to more than 300 cm in the Cascade Range and summers are dry and warm with winters cloudy and wet. Daily average temperatures in the basin range from 1.7°C in winter to 28°C in summer. A cross-sectional profile of the basin is shown in Figure 2A. Figure 2B identifies specific morphological reaches of the main stem Willamette River. 2

Dissolved Oxygen - A Quantitative Investigation Background. Through the early 1950s, the Willamette River experienced severe water quality problems based primarily on dissolved oxygen (DO) deficits created by a combination of summertime low-flow conditions and oxygen demanding wastes discharged from municipal and industrial sources. The low DOs (0 - 4 mg L' ) resulted in serious impacts on many beneficial uses of the river; fish survival and migration, aesthetic appeal, recreation, industrial use and potential drinking water quality all suffered. Over the course of three decades from 1950 through 1980 water quality was improved 1

Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992.


THE SCIENCE OF GLOBAL CHANGE

Figure 1. Map of the Willamette River Basin, Oregon, showing major physiographic divisions and the Molalla River basin (shaded).


13 DUNNETTE

Mechanistic Approaches to River Water Quality 263 — HIGH CASCADES

•


Figure 2A. Cross-sectional profile of the Willamette River Basin showing relief dimensions of major physiographic divisions.

DISTANCE. IN RIVER MILES ABOVE MOUTH I 300

ι

ι 200

ι

ι 100

I

I 0

DISTANCE, IN RIVER KILOMETRES ABOVE MOUTH

Figure 2B. Willamette River, Oregon showing gradient and morphological reaches.


264



dramatically due to reduction of waste loading to the river and flow augmentation from headwater reservoirs (see Figure 1). The dissolved oxygen investigations described here had two primary goals: to document the improvement in Willamette River water quality and to develop an understanding of the physical, biochemical and biological dynamics of the DO regime of the Willamette River which could be applied to river basin planning and management. Methodology. The design of this investigation was based on the philosophy expressed in the previous chapter, i.e., that a mechanistic or intensive survey approach can most effectively provide the understanding which will permit development of reliable basin management control alternatives. Reconnaissance studies were initially carried out to obtain preliminary measurements of DO, biochemical oxygen demand (BOD), nitrification, sedimentary oxygen demand (in Portland reach), photosynthesis and reaeration as well as the magnitude of municipal and industrial oxygen demanding wastes. DO investigations were conducted during the summer low-flow, a period of relative ecological stability. Standardized methods were used and 3 to 6 samples were collected at each site selected. Details of methodology are provided elsewhere (6-13). Results. Total point and non-point source B O D (20 day BOD incubation) loading to the river between river kilometer (RK) 300 and 0 was 77,000 kg d" with point sources contributing 54% and nonpoint sources 46%. Seventy-six percent of B O D loading was exerted in the shallow upstream reach between the RKs 300 and 84. In addition to these carbonaceous based oxygen demands, nitrification accounted for an estimated additional 31,000 kg d" loss of oxygen, almost all of which occurred between RKs 140 and 89, the most "surface active" reach of the main stem Willamette River. Carbonaceous deoxygenation between RKs 140 and 89 accounted for 40,000 kg d" of DO loss with sedimentary demand estimated at 12,000 kg d . Figure 3 summarizes DO data for an intensive survey conducted during low-flow. The dramatic drop in DO between RKs 194 and 81 was determined to be due mainly to microbially mediated in-stream nitrification of 3,300 - 6,200 kg d" ammonia Ν discharged from a pulp and paper plant at R K 140. The increase in DO at R K 47 is due to the combined effects of reaeration at Willamette Falls and a contribution from the highly oxygenated Clackamas River. The drop in DO below R K 32 was found to be due largely to sedimentary oxygen demand in the Portland reach where organically enriched material is deposited. Recovery below R K 6.5 was due to a combination of reduced oxygen demanding waste loading and mixing with Columbia River water. Reaeration coefficients calculated from hydrologie data varied from 2.0 in the upper river to a low of 0.003 in the lower river near Portland. A nitrification rate constant of 0.7 day" for R K 140 - 89 was estimated from changes in nitrate concentrations. DO measurements taken during operation and closure a pulp and paper ult

1

ult

1

1

1

1

1



13 DUNNETTE

Mechanistic Approaches to River Water Quality 265

plant indicated a drop in DO of 3-4% saturation 5 K M below the plant. An analysis of dissolved oxygen saturation of the lower river during the period 1973-1979 indicates the 15% increase in DO in the lower Willamette is primarily a result of the elimination of the industrial ammonia discharge at R K 136. Improvement in DO in the Willamette River was due principally to the ammonia source elimination in 1977 (Figure 4). A DO computer model was developed using the accounting method of Velz and a simple Lagrangian reference system (9, 12). A sensitivity analysis of the model is provided in Table 1 (12). Results indicate that model projections are most sensitive to flow, initial DO, reaeration method calculation, ammonia loading and sedimentary oxygen demand and are relatively insensitive to BOD load variations, BOD rates and nitrification rates. Verification of model projections based on sampling results (diurnally normalized) is summarized in Table 2 (8). Figures 5, 6 and 7 illustrate typical model output which can be translated directly into river basin planning strategies (12). Conclusions - Dissolved Oxygen. Continued attainment of DO standards in the Willamette Basin in the face of a current regional growth rate of 1% yr" will require continued augmentation of flow as well as pollution control, particularly with respect to ammonia. Based on model results discussed, there appears to be little justification for the installation of advanced wastewater treatment systems in the basin for the purpose of maintaining acceptable DO levels. 1

Erosion/Deposition - A Semi-quantitative Investigation Introduction. Disintegration and erosion of surface layers of the world's soils may be the most severe of the environmental impacts caused by human

187

134

86.5

50

39

34

RIVER MILES ABOVE MOUTH 28.6 17 12.8 10

7.0

6.0

3.5

1.5

TIME OF TRAVEL, IN DAYS

Figure 3. Dissolved oxygen profile of Willamette River, low flow conditions, 1973 with major DO controlling factors. Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

0

Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992. 1

1

Model is relatively insensitive to B O D load variations. A doubling of loads (from each point source) results in deviations of 5-9 percent DO saturation from the standard profile.

BOD loading

ult

Model is sensitive to the method used to calculate reaeration. Only the Velz method gave segment-by-segment reaeration inputs which resulted in good agreement of predicted and observed DO profiles.

For the reasonably expected range of summertime water temperatures, the model is insensitive to temperature changes. Maximum predicted deviation from standard conditions is +. 3 percent of DO saturation.

1

1

1

Reaeration calculation method

Water temperature

boundary point (RK 140)

1

1

Model is sensitive to changes in initial percent of DO saturation. The major impact is near the boundary point; differences between profiles become smaller with downstream distance.

1

1

Percent DO saturation at

1

Model is sensitive to flow, particularly at values less than 328 mV (6,760 ftV ). At 243 mV (5,000 ftV ), predicted percent DO saturations are as much as 10 percent less than those at 328 mV (6,760 ftV ). At 158 mV (6,760 ftV ' estimated natural low flow), predicted values are as much as 30 percent lower than standard conditions. At 437 mV (9,000 ftV ), predicted values are higher by 6-8 percent saturation.

Comments

Streamflow

Variable tested

Table 1. Sensitivity Analysis Summary Of DO Model



The model is sensitive to lower river sediment oxygen demand. If the demand is removed, the predicted DO value at R K 3.1 (RM 5.0) is 8 percent higher than the standard condition.

Benthic demand

Source: (13)

Model is insensitive to expected range of changes in summertime water depth in the tidal reaC.H. Predicted DO values differ from standard profile by an average of 1 percent saturation.

n

Variation in water depth owing to backwater or tidal influences

n

Model is insensitive to changes in k„ over a range of 0.5-0.9 day" . Predicted DO concentrations differ from standard profile (k = 0.7) by less than 3 percent. Note that differences decrease with downstream distance.

Rate of nitrogenous deoxygenation (k )

1

Model is sensitive to variations in ammonia-N loading. A doubling of loads (from outfalls in the nitrifying segment) results in as much as a 14 percent reduction in percent DO saturation values from the standard profile. Reducing the ammonia loading by 50 percent increases the predicted DO values by up to 8 percent saturation.

1

Arnmonia-N loading

r

r

Model is relatively insensitive to changes in k over a three-fold range of 0.02-0.06 day . Predicted DO concentrations deviate no more than 6 percent saturation from standard profile.

Rate of carbonaceous deoxygenations (k )


268

THE SCIENCE OF GLOBAL CHANGE River

kilometers

above mouth Willamette

100

150

Salem

Newberg

falls 50 j

100

^Portland^ *~ harbor*"

"Τ

90 h

c g

2 δ (Λ


80

c Φ ο» Ό

70

>

6000 cfs Salem

Ο «Λ «Λ

Explanation State DO standard

60

100

80

60

20

40

River miles above

mouth

Figure 4. Dissolved oxygen profile of Lower Willamette River, low flow conditions. Data points are means of 4-6 samples, diurnally normalized. Table 2. Verification of Willamette River DO Model

Location

RK

Model results Projection % sat.

Wheatland Ferry Newberg Oregon City Portland Portland

116 89 46 19 8.1

89 86 88 87 78

a

RK 116 78 44 19 11

3

DEQ Results Verification Measured % sat 90 90 89 86 79

Mean of 23 weekly grab samples collected during months of July, August and September, mean flow of 184 m V at Salem. DEQ values have been diurnally normalized. Source: (8) 1




DUNNETTE

Figure 6. Dissolved oxygen for various streamflows. Point source ammonia and BOD loading constant. Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

270



Figure 7. Dissolved oxygen for various point-source ammonia loadings. Flow constant at 6000 ftV . BOD and NPS ammonia loading held constant. 1


13 DUNNETTE


activity. In the Willamette basin the form and character of the land is determined primarily by natural characteristics of the land and rainfall patterns. Over the past 165 years, humans in the Willamette Basin have shifted ecological equilibria with multifaceted land activities, many of which have direct influences on rivers. The Molalla River basin, a subbasin of the Willamette system (Figure 1) covers about 840 km (325 mi ) and was used as a model basin to demonstrate use of an erosion/ deposition impact matrix and map. Altitudes in the basin vary from 15 m to 1500 m. The major industries are forestry and agriculture. Precipitation varies from 1000 mm (40 in) in the lowlands to 3000 mm (110 in) in the headwaters with temperatures ranging seasonally from over 38°C to well below 0°C. Average annual runoff varies from less than 500 to over 2500 mm (20 to 100 in) per year. Over two-thirds of the basin has a slope which exceeds 20 percent. The basin is underlain by volcanic rocks in the higher elevations, sedimentary materials in the lowlands and is dominated with conifers of the Douglas Fir variety although alder, oak, shrubs and grasses also occur. Over 80 percent of the higher elevation forest lands have been clearcut and Figures 8 and 9 illustrate the impact of this particularly destructive form of land use activity in the Molalla River basin. More detailed geologic, climatic and topographic data may be found elsewhere (14).


2

2

Erosion/Deposition Impact Matrix and Map. Methods applied in this semi quantitative assessment involved mapping depositional features using high and low altitude imagery, numerical ranking of land use activity impacts and construction of problem matrixes. The information generated in these first steps were applied to the Universal Soil Loss Equation (15-16). A = RKLSCP

(1) 1

where A = average annual soil loss, in tons acre^/year" Β = rainfall coefficient Κ = soil erodibility coefficient L = slope-length coefficient S = slope-steepness coefficient and C & Ρ = coefficients related to conservation practices and land use The rationale for the development and application of the matrix was established 20 to 25 years ago and is discussed elsewhere (14,17). The location and density of land erosion and deposition features were identified through intensive analysis of stereoscopically paired color infra-red images at a scale of 1:130,000. The observations made from the color infra-red analysis were systematically noted and verified through field observation and low altitude imagery (14). Results. Using the information generated in the analysis, an erosion/deposition impact matrix was developed as shown in Table 3 (14,15). The horizontal axis



3

3

2

1

1

1

1

1

3

3

1

2

IO"

io-

1

1

1

1

2

2

1

1

1

2

2

2

2

2

2

3

Iff IO" Iff Iff Iff 3

2

3

io2

3

3

2

2

2

3

3

3

IO" IO" IO" Iff Iff Iff IO" IO" Iff Iff Iff Iff

io2

3

3

60 10


2

1

1

10° 10 10 IO 10 Iff 10° 10°

1

1

1

1

Iff 10° 10° 10 10 1

1

1

Iff 10° 10° 10 10 2

2

1

1

2

2

1

1

10° 10° 10 10 10 10 10 10 10 10 3

3

2

2

1

10 10 10 10 10

2

3

2

x

2

3

3

2

2

1

10 10 10 10 10

^-Surficial, weakly coherent, alluvial deposits readily eroded by water. percent slope; V -10 3

2

3

3

3

10 10 10 >10 >10 3

3

3

3

3

10 >10 >10 >10 >10


274


Figure 8. Clear-cut in the Molalla River Basin showing tractor logging practice and erosion surfaces.

Figure 9. Massive landslide near headwaters of the Molalla River, Oregon, a tributary of the Willamette River. The landslide occurred on the lower slope during the winter following the building of two log roads associated with clear-cutting activity. Dunnette and O'Brien; The Science of Global Change ACS Symposium Series; American Chemical Society: Washington, DC, 1992.


13 DUNNETTE


consists of assigned factors related to geology and slope whereas the vertical axis lists impact factors assigned to various land-use activities. The values in the matrix are products of geology, slope and land use and represent semiquantitative estimates of potential impact given the various conditions of slope, geology and human activities. Values are expressed in terms of tons per acre year. The results of map generation cannot be expressed effectively with the format available here. However, the State of Oregon utilized the map and matrix techniques in their nonpoint source evaluation and as a basis for designing more intensive survey approaches to assessing the impact of human activity on river quality. In addition to reflecting deposition of sediments, the methods can be applied to transport of pesticides, nutrients and trace elements since many of these substances tend to adsorb to the organic and inorganic fractions of soil. Potentially Toxic Trace Elements - A Qualitative Approach Introduction. A number of chemical substances in the aquatic environment have been identified as toxic to living organisms. Such substances include pesticides, herbicides and certain trace elements. Concern for these substances is based on a complex set of factors leading to the public's perception that certain chemical forms in the environment are dangerous. Although many of the substances identified as toxic are essential nutrients including chromium, copper, zinc, and selenium, little attention is often given to Paracelsus' corollary that the dose makes the poison (i.e., that risk is a function of both intrinsic hazard and exposure), that trace elements in the environment occur naturally in soil and rocks, or that all humans ingest these substances continuously in doses ranging from a few micrograms (mercury) to several milligrams (copper, zinc) per day. The question of potential harm to aquatic life or human health from the presence of certain trace elements in rivers is extremely complex and is discussed in the previous chapter. The reader is referred to recent sources which discuss risks related to environmental chemicals (18-20). The Willamette River basin is bounded on the west by the Coast Range and on the East by the Cascade Range. The volcanics of the Cascade Range consist of basalt and andésite. The Coast Range and its foothills are composed largely of sedimentary material of both volcanic and marine origins including basaltic materials, mudstone, shale, and sandstone. The Willamette valley lowlands are composed of terrace deposits of sand, silt and clay. The basin is not highly industrialized and the major oxygen demanding wastes entering the main stem originate from pulp and paper companies and municipal wastewater treatment plants. There are a number of mineralized areas in the southeastern part of the basin which have produced quantities of copper, gold, silver, lead, mercury and zinc. The goals of the investigation reported here were to determine 1) the concentrations of trace elements in water, fish and other indicator media in the Willamette River system and 2) what evidence or


276



documentation exists which indicates or suggests harm to humans or aquatic life. Methods. As discussed in the previous chapter, a number of approaches have been used to assess the presence of potentially toxic trace elements in water. The approaches used in this assessment include comparative media evaluation, a human health and aquatic life guidelines assessment, a mass balance evaluation, probability plots, and toxicity bioassays. Concentrations of trace elements were determined by atomic absorption spectrometry according to standard methods (21,22) by the Oregon State Department of Environmental Quality and the U.S. Geological Survey. Sampling sites for water, sediment andfishwere distributed along the main stem Willamette. Water data are based on a total of 12 monthly samples for each of the twelve sites (DEQ data) or quarterly samples over a period of 4 years (USGS data). Sediment samples were taken from 44 different sites covering the entire main stem Willamette River. The

Chromium Max 20 Min

Assessing Global River Water Quality - ACS Publications - American

Recommend Documents