Regionally Based Clean Water Activities: Work Plan and Proposal

Regionally Based Clean Water Activities: Work Plan and Proposal

A Proposal Submitted to
U.S. Environmental Protection Agency
July 2005

Submitted by
Desert Research Institute
University and Community College System of Nevada

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CONTENTS

LIST OF FIGURES

LIST OF TABLES

I. PROBLEM STATEMENT

II. OBJECTIVES

III. SUMMARY OF TASKS

Task A. Periphyton Distributions, Dynamics, and Environmental Controls in Nevada

Task A.1: Periphyton Distributions and Dynamics

Task A.2: Temperature Response of Photosynthesis, Respiration, and Growth

Task A.3: Reach-scale Groundwater-Surface Water Exchange as a Regulator of Periphyton Dynamics

Task B. Benthic Macroinvertebrate and Periphyton Communities Related to Sediment Loading in the Lower Truckee River

Task C. High-resolution LIDAR and Hyperspectral Remote Sensing of Rivers in Western Nevada

Task C.1: Mapping Streamside Vegetation

Task C.2: Aquatic Vegetation

Task D. Simulation Modeling Studies in Support of Management to Protect Beneficial Uses and Nutrient Criteria Development

Task E. Public Outreach

Task F. Quality Assurance Project Plan

IV. SIGNIFICANCE OF RESEARCH AND PUBLIC BENEFITS

REFERENCES

BUDGET SUMMARY AND JUSTIFICATION

KEY PERSONNEL

LIST OF FIGURES

1. Conceptual model of biomass and primary producer dynamics

2. Truckee River - August 2002. a) Biomass of periphyton and b) dissolved inorganic nitrogen (DIN) and orthophosphorous.

3. Periphyton biomass on cobble substrates (expressed as chlorophyll a; Chla) in the LTR from August 2000 to July 2001.

4. Periphyton biomass on cobble substrates (expressed as chlorophyll a; Chla) in the LTR from October 2001 to August 2002.

5.Dissolved oxygen concentrations at the monitoring site (Tracy) closest to the location of the periphyton peak shown in June 2002.

6.Regions of abundant periphyton growth in meandering rivers.

7.Carson River Basin.

8. Nodal structure of DSSAMt with tributaries and withdrawals for irrigation and municipal industrial uses (Brock et al., 2004)

9. Riffle-pool sequence in a sinuous channel showing definition of features.

10.A typical hydraulic reach in a river water quality model composed of multiple riffle-pool units.

LIST OF TABLES

1.Numerical water quality models for dissolved oxygen and temperature that have been applied to the Truckee and Carson rivers.

2. Generalized nutrient regimes for the Truckee River.

3.Relation of proposed research to ongoing DRI projects.

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I. PROBLEM STATEMENT

State and local agencies in Nevada are currently under intense pressure to meet conditions of the Clean Water Act (CWA); particularly those related to nonpoint source pollution (Section 319[h]), impaired waters (Section 303[d]) and associated total maximum daily loads (TMDLs). Among the challenges facing the state are sparse data, inadequate scientific basis for existing water quality standards, a general lack of decision-making tools such as models and spatial analysis software, and insufficient financial resources to support in-house technical staff. Discussions with state and local stakeholders (e.g., Nevada Division of Environmental Protection, or NDEP; Pyramid Lake Paiute Tribe; and Washoe County) along with staff from U.S. Environmental Protection Agency’s (EPA) Region IX have helped identify and prioritize a suite of water quality-related activities that address some of the aforementioned water quality challenges. The geographic focus of these activities includes three western Nevada river basins (the Truckee, Carson, and Humboldt rivers). The scientific focus will involve a suite of laboratory and field-scale activities designed to better understand the effects of natural and human factors on ecological function in western river basins. A unifying element for data derived from this research will be application to one or more numerical water quality models, which will lead to improved capability to simulate future conditions under varying management scenarios.

Background

Nutrient-Dissolved Oxygen Dynamics in Western Nevada Rivers

At their lower elevations, rivers in the Great Basin ecoregion of western Nevada tend to be shallow, with minimal shading from riparian vegetation. Depending on local conditions of turbidity, solar radiation can reach the bottom in riffle sections, and, provided other conditions are favorable (temperature, nutrients), attached algae (periphyton) or rooted vascular plants can serve as the dominant primary producers. In these riverine ecosystems, most metabolic activity is associated with benthic processes because the rivers are not sufficiently deep, nor residence time long enough, to support development of phytoplankton communities. Significant biomass of aquatic vegetation and associated detritus can accumulate in reaches where nutrients are sufficient and conditions such as irradiance and bed material (substratum) are favorable. These endogenous accumulations of organic material can lead to substandard oxygen conditions, especially during periods of low flow and elevated temperatures in summer.

A common trait of many water quality models that have been developed for use in western Nevada (see Table 1) is that they simulate in-stream dissolved oxygen (DO) as a function of periphyton biomass dynamics (photosynthesis and respiration). A substantial portion of the uncertainty associated with DO simulation and prediction relates to our inability to fully characterize the complex relationships between periphyton biomass production and external inputs such as nutrients, temperature, hydraulics, light, grazing, and substrate conditions.

The DO regime is a primary characteristic that defines water quality in rivers and is determined by the magnitude of oxygen-demanding and oxygen-producing processes and substances that impact a parcel of water. These factors can be physical (e.g., reaeration across the air-water interface), as well as chemical, and biological. The relative contribution of DO controlling factors varies among rivers based on their size, channel characteristics, and the nature of their inputs. In shallow rivers with sufficient nutrients, abundant in-stream growth of primary producers can lead to accumulations of organic matter and low DO conditions, provided other factors are conducive.

Table 1.Numerical water quality models for dissolved oxygen and temperature that have been applied to the Truckee and Carson rivers.

Our conceptual model for the balance between photosynthesis (i.e., primary productivity) and respiration-removal in a river segment is determined by a suite of factors (also known as drivers) that interact in a complex fashion (see Figure 1). Photosynthesis and respiration-removal rates are determined by drivers that are physical (e.g., irradiance, temperature, scour, turbulence, and available substrate), chemical (e.g., nutrients, pH), and

Figure 1. Conceptual model of biomass and primary producer dynamics (RESP = Respiration and Temp = Temperature).

biological (herbivory and community dynamics). The net balance between productivity and respiration-removal processes results in a standing crop of primary producer biomass that can be a critical determinant of DO levels in a river. The primary drivers affecting primary producer biomass in rivers are typically thought to be physical and chemical (left side of Figure 1). However, in some systems during specific seasons, top-down control may exert a significant effect on primary producer biomass through herbivory (grazing).

Substratum for primary producers varies with the nature of the riverine ecosystem, and in general terms can be comprised of either bed material or biological features such as emergent vascular plants that provide a surface for the development of epiphytic algae. When substratum is dominated by bed material, its suitability as a growth medium for benthic algae varies as a function of particle size (e.g., silt, sand, cobble) and associated mobility of the particles.

Extensive attempts over the past few decades to predict primary producer dynamics based on simple relationships among these variables have met with limited success (e.g., Bott et al., 1985; Dodds et al., 2002). However, there tends to be some general constraining factors that affect biomass dynamics on a coarse resolution basis. Examples include the following:

• Under conditions where irradiance or essential nutrients are lacking, algae will not accumulate beyond low biomass levels. In a river system with an oligotrophic natural lake or impoundment (e.g., the Upper Truckee River downstream from Lake Tahoe; the Kootenai River in northern Idaho below Libby Dam), one observes low phosphorous conditions and low biomass of attached algae.
• Rivers with elevated suspended sediment concentrations (e.g., those draining mountainous glaciated regions) or dark color (e.g., blackwater rivers) may have low primary productivity due to the highly attenuated irradiance.

Rivers traveling through urban areas often have large inputs of dissolved chemicals that lead to the development of large spatial gradients in some constituents (Figures 2a and 2b). These inputs are largely due to anthropogenic inputs but can also be the result of changes in geologic features along the river. Irrespective of the cause, these large inputs can promote biostimulation in downstream reaches of the river. Elevated nutrients lead to an increased standing crop of algae and higher trophic levels such as benthic macroinvertebrates. Figure 2b depicts the profile of dissolved inorganic nitrogen (DIN) and orthophosphorous in the Truckee River during August 2002. The spike in nutrient concentration at about 100 km is associated with loads from agricultural return drains, urban runoff, and treated wastewater from the Reno-Sparks metropolitan area. The typical nutrient regime during base-flow conditions in the Truckee River is characterized in Table 2. The upper 40-km reach (zone i) has orthophosphorous concentrations below those thought to saturate growth of attached algae in rivers (~0.030 mg/L; Bothwell, 1989). Conversely, the lower section of the river within zone iv has DIN concentrations (0.019 mg/L; Biggs, 2000) below those levels at which biomass of non-nitrogen fixing algae may be controlled below “excessive” levels (Welch et al., 1988).

The downstream trend in standing crop of attached algae in the Truckee River for August 2002 suggests an apparent biostimulatory response to nutrient loading near km 100 (Figure 2a). In this nutrient zone iii, both inorganic nitrogen and orthophosphorous are in ample supply. Under conditions when a nutrient is limited (zones i and iv), the variability in biomass tends to be lower than where nutrients are in ample supply (zone iii). The response of periphyton to nutrient concentration observed on the Truckee supports Liebig’s law of the minimum, which is fundamental to the algorithms used to numerically simulate primary productivity in mechanistic models. According to Liebig’s law, the total yield, or biomass, of an organism will be determined by the nutrient present in the lowest (minimum) concentration in relation to the requirements of that organism. In areas where nutrients are ample (zones ii and iii), factors other than nutrients (e.g., temperature, flow, scour, turbulence, herbivory) will limit periphyton growth. These drivers tend to exhibit a range of conditions based on microhabitats determined by geomorphologic conditions of the fluvial channel.

Figure 2.Truckee River - August 2002. a) Biomass of periphyton and b) dissolved inorganic nitrogen (DIN) and orthophosphorous. Error bars represent 1 SE (n = 11 to 20). The cities of Reno and Sparks as well as agricultural areas are located in the Truckee Meadows between km 90 to 105. Nutrient zones are represented by dashed arrows (see Table 2).

Table 2. Generalized nutrient regimes for the Truckee River. Concentrations shown in bold are generally considered limiting of algal growth.

Generally, there is a positive correlation between nutrient concentration in the water column and benthic algal biomass. A recent comprehensive study by Tank and Dodds (2003) illustrated the complexity of periphyton dynamics in streams. They reported results of controlled experiments with nutrient-diffusing substrates simulating 10 streams with eight different biomes representing a range of rivers from the tropics to the arctic. They observed threshold values of nutrients below which nutrient limitation may be observed. However, factors other than nutrients tend to exert a strong influence on the accumulation and distribution of algal biomass. Nonequilibrium conditions and habitat heterogeneity in temperate streams can produce environmental noise that results in a statistical variance in algal-nutrient relationships that is greater in flowing aquatic ecosystems compared with lakes. In an evaluation of a large number (n = 620) of stream locations, Dodds et al. (2002) found that nutrients accounted for less that half of the variance in benthic algal biomass. Factors such as hydraulic conditions, flow, light availability, and grazing were thought by Dodds et al. (2002) to be responsible for the remaining variability in benthic algal biomass. Improved predictive ability was achieved in detailed studies of periphyton biomass that accounted for nutrient concentration as well as hydrologic parameters (especially length of time since the last flood), land use, and geology (Lohman et al., 1992; Biggs, 1995).

The U.S. Environmental Protection Agency (1998) initiated the process of developing nutrient criteria for water bodies that would serve as the basis for setting total maximum daily loads (TMDLs) for nutrients. It then developed national nutrient criteria recommendations based on ecoregions, but encouraged states and tribes to critically evaluate and refine these recommendations at the regional level. California, Arizona, and Nevada formulated a Regional Technical Advisory Group (RTAG) for developing criteria for EPA Region IX. One of the initial activities of the RTAG was a pilot project to evaluate regional reference conditions for streams and rivers in aggregated Ecoregion II (Western Forested Mountains). The results of the pilot project underscored the importance of refining nutrient criteria on a regional basis, because application of the national criteria in the pilot project resulted in significant misclassification of reference streams. (A large number of minimally impacted sites were classified as impacted using the national criteria.) In Region IX, there is a wide range in nutrient levels found in minimally impacted aquatic systems (Tetra Tech, 2000). Development of appropriate nutrient criteria to limit algal biomass to acceptable levels requires better understanding of the interplay between nutrient overenrichment and the other factors that contribute to reducing algal growth and losses as illustrated by our conceptual model (Figure 1).

Applications of ecological water quality models to predictions of DO and periphyton have demonstrated significant divergence when simulated results are analyzed against observed data. The ability to model periphyton and DO in rivers has been hampered by our lack of understanding of relationships among the variables shown in Figure 1. The uncertainties in our understanding of periphyton dynamics serve as the underlying theme in this work plan for clean water activities in western Nevada.

II. OBJECTIVES

With the above as background, the objectives of the work to be completed under the cooperative agreement are as follows:

1. to develop the physical and biological basis for improving existing models and other management tools for use in western Nevada watersheds though a variety of workplan tasks that address algal (periphyton) kinetics, benthic macro invertebrates; hydrologic processes, and image analysis;
2. to integrate newly acquired experimental and field results using the numerical simulation model(s) as the unifying platform;
3. to operate the amended models under a variety of input (anthropogenic and natural) scenarios;
4. to improve the information base for evaluating and applying existing water quality models; and
5. to improve the capacity of water managers to identify water quality issues related to algal growth in western streams.

III. SUMMARY OF TASKS

The workplan elements, or tasks, described below are intended to address many of the complex relationships noted earlier, and will lead to an improved understanding of those factors influencing water quality in western watersheds. A common theme among tasks A.1 through A.3 is that of periphyton biomass, its impact on in-stream dissolved oxygen, and improving our understanding of physical and chemical processes that impact primary productivity and our associated ability to model and predict water quality under varying land- and water-use scenarios. Task B focuses on the relationship between benthic macro-invertebrate communities and suspended solids. Task C focuses on the acquisition and analysis of remotely sensed data within the Carson River basin. Task D describes the integration of data and results generated under Tasks A-C through the direct application of numerical simulation models to beneficial use and nutrient criteria issues in western Nevada. Task E describes the public outreach and data sharing aspects of the project.

Currently, DRI researchers are directly involved in several applied and basic research or monitoring programs within the proposed study areas. Table 3 provides a brief description of each, including potential linkages between these ongoing projects and the activities proposed in this work plan.

Table 3.Relation of proposed research to ongoing DRI projects.

Task A. Periphyton Distributions, Dynamics, and Environmental Controls in Nevada

Background