Long-term monitoring and research of the ecology of the Tres Rios constructed treatment wetland, Phoenix, AZ, ongoing since 2011
Publication date: 2020-08-12
Author(s):
- Dan Childers, Arizona State University
- Dax Mackay, Arizona State University
- Christopher Sanchez
- Nicholas Weller
Abstract:
# Project Description
In order to better understand the water, nutrient and treatment dynamics of aridland constructed treatment wetlands, we have developed datasets tracking primary productivity (aboveground and belowground), nutrient and water budget dynamics, soils, and aquatic metabolism at the Tres Rios wetlands, operated by the City of Phoenix Water Services Department, since July 2011. The 3-cell Tres Rios Wetlands were completed in 2010 and are associated with the 91st Avenue Wastewater Treatment Plant, the largest in Phoenix. This project is focused on the largest of the three wetlands treatment cells which was the first to be planted and became operational in Summer 2010. The wetland cells are bounded by roads (the "shoreline"), and the system we study is 42 ha in size, approximately half of which is open water and half of which is fringing vegetated marsh. Water depth is relatively consistent across the marsh (approximately 25cm) and effluent inflow to the cell varies seasonally from 95,000 to over 270,000 m3 d-1. Measurements are taken along two gradients representing the two hydraulic pathways of the system: The whole-system, from inflow to outflow, within the vegetated marsh itself.
# Abstract
Constructed treatment wetlands (CTW) provide cost effective and ecosystem-service based solutions to the problem of urban wastewater treatment. They are a particularly attractive option for water reuse in arid cities, where water resources are scarce, and understanding CTW function in these environments is critical to facilitating sustainable water use practices. Although CTW are well established and studied in mesic climates, how they function in and respond to hot, arid climates is comparatively not well understood. Specifically, large atmospheric water losses via evaporation and plant transpiration comprise a much larger component of the whole-system water budget than in mesic climates. Additionally, given the primary role that emergent macrophytes play in nitrogen removal, the effects of plant community composition and primary productivity patterns on system performance in the context of aridland constructed treatment wetlands have not been extensively studied. Our goal is to develop a model of how these "working wetlands" perform in arid climates by developing and comparing nutrient and water budgets. At the Tres Rios constructed treatment wetland in Phoenix, AZ, USA, we measure atmospheric water losses via plant transpiration and open water evaporation as well as inorganic nitrogen fluxes at the whole system and the vegetated marsh scales. Total water losses via evaporative pathways peaked at 300,000 m3 per mo-1 (714 L H2O m-2 mo-1) in the hot summer months and represented more than 70% of the whole-system water budget over a 27 month time period. These evaporative losses are nearly an order or magnitude higher than rates observed in mesic systems. Peaks in above-ground biomass ranged from 1586±179 to 2666±164 gdw m-2, with Typha spp. accounting for up to two-thirds of total biomass. Overall, the vegetated marsh removed almost all of the inorganic N supplied to it, and large transpirative water losses were observed to move large volumes of replacement water into the marsh via a plant-mediated "biological tide." This process providing additional opportunities for soil microbes and emergent macrophytes to process target solutes, and potentially enhancing the treatment efficacy of the aridland Tres Rios constructed treatment wetland relative to more humid and mesic systems.
Keywords:
wetlands,
biomass,
evaporation,
evapotranspiration,
primary productivity,
water quality,
nutrients,
nitrogen,
phosphorus,
gas flux,
transpiration primary production,
movement of organic matter,
movement of inorganic matter,
water and fluxes,
parks and rivers tres rios,
treatment wetlands,
constructed wetlands cap lter,
cap,
caplter,
central arizona phoenix long term ecological research,
arizona,
az,
arid land
Temporal Coverage:
2011-07-01 to 2020-07-22
Geographic Coverage:
Geographic Description: CAP LTER study area
Bounding Coordinates:
Longitude:-112.266838 to -112.261501
Latitude:33.398637 to 33.388571
Contact:
Information Manager, Central Arizona–Phoenix LTER,
Arizona State University,Global Institute of Sustainability,Tempe
caplter.data@asu.edu
Methods used in producing this dataset:
Show
# Transpiration
Leaf-specific transpiration rates were measured using a LICOR LI-6400 infrared gas analyzer bi-monthly along marsh transects that contained all species groups. Measurements were made on individual plant leaves at 50-cm intervals from the water surface to the top of the plant canopy. Where plants did not have leaves but only thick stems (Schoenoplectus spp.), we used custom-made extensions of the stock LI-6400 IRGA sampling chamber to ensure an airtight seal without damaging plant tissue. Gas flux data were collected on one transect at a time from sunrise until as late as possible. These data included measurements of leaf-specific transpiration rate (Tr mmol H m-2 sec -1), photosynthetically active radiation (PAR, μmol photons), relative humidity (%), and ambient air temperature (degrees celsius), all of which were captured using the IRGA's default sensors. While the IRGA reports transpiration data in units of leaf surface area, we expressed them in units of dry weight biomass by weighing 8-10 samples of different tissue samples from the IRGA's chamber and generating relationships between dry weight biomass and surface area for all plant species.
To scale the daily plant-specific transpiration measurements across space, IRGA measurements corrected for dry-weight biomass we to re combined with whole system live macrophyte biomass estimates as calculated by the bimonthly data collected along the 10 sampling transects (see biomass section for details). To scale the plant-specific measurements in time, micrometeorological data as collected by the IRGA at the time of transpiration sampling were regressed with simultaneous data from an on-site meteorological station operated by the City of Phoenix. In addition, as plant transpiration in Tres Rios is largely driven by temperature, photosynthetically active radiation, and humidity, we regressed plant transpiration rates against these variables to be able to predict transpiration using meteorological data. Combined with the IRGA-meteorological station regressions, these models allowed us to interpolate our plant-specific measurements through time, resulting in total transpiration losses for the whole system (m3/mo-1). See Sanchez et al. (2016; DOI: 10.1016/j.ecoleng.2016.01.002) for more details.
# Biomass
We used a point intercept transect approach across 10 approximately 50m transects that were evenly distributed across the wetland cell from inflow to outflow. Every two months we measured live aboveground biomass in five 0.25m2 quadrats that were randomly distributed along each transect. In each quadrat, we measured plant culm and various plant characteristics (stem height, number of leaves, etc.) and converted these measurements to dry weight biomass for each plant using established phenometric biomass models (see Weller et al. 2016 (DOI: 10.1016/j.ecoleng.2015.05.044) for more detail). Plant weights in each quadrat were summed for each quadrat. These measurements were scaled to the whole-system by averaging quadrat-specific estimates across each transect, multiplying by 1/10th of the total vegetated area (21ha), and summing across all transects.
# Water Quality
We used a point intercept transect approach across 10 approximately 50m transects that were evenly distributed across the wetland cell from inflow to outflow. These are the same transects used for biomass measurements. Bimonthly triplicate surface water grab samples were collected at the whole-system inflow and outflow using acid-washed 1 L Nalgene bottles, while single grab samples were collected at the beginning and end of each transect. A Lachat QC 8000 Quickchem Flow Injection Analyzer (detection limit 0.85 μg NO3-N L-1 and 3.01 μg NH4- N L-1) was used to centrifuge and analyze unfiltered samples for inorganic nitrogen (NO3-, NO2-, and NH4+) and soluble reactive phosphorus (SRP, PO4-3). At the sample locations where grab samples were taken, a YSI Pro 2030 meter was used to measure conductance and temperature while a YSI Ecosense ph100 meter was used to measure pH.
Data Files (4) :
Tabular:
633_plant_attributes_d4550e6c0e389edb7956f5c773bb5aef.csv
Description: Tres Rios: indices of primary productivity. Measurements of various physiological characteristics of individual plants located within study transects at the Tres Rios wetlands. These data are used as inputs into biomass models to calculate above-ground primary productivity.
Column |
Description |
Type |
Units |
date |
date of observation
|
date |
Format: YYYY-MM-DD |
transect |
transect ID
|
string |
|
quadrat |
location of quadrat along transect
|
string |
|
species |
plant species
|
string |
Enumeration:
-
s_acutus: Schoenoplectus acutus
-
s_americanus: Schoenoplectus americanus
-
s_californicus: Schoenoplectus californicus
-
s_maritimus: Schoenoplectus maritimus
-
s_tabernaemontani: Schoenoplectus tabernaemontani
-
t_domingensis: Typha domingensis
-
t_latifolia: Typha latifolia
|
plant_id |
plant id (for linking to Typha leaves data)
|
string |
|
cdb |
Culm diameter of plant stem taken at water surface
|
float |
centimeter |
stem_height |
Height of plant stem (Schoenoplectus spp. Only)
|
float |
centimeter |
num_seed_stems |
Count of seed steams at plant tip (Schoenoplectus spp. Only)
|
float |
number |
pistillate_length |
Length of pistillate, if present (Typha spp. Only)
|
float |
centimeter |
pistillate_width |
Width of pistillate, if present (Typha spp. Only)
|
float |
centimeter |
data_book_ID |
field data book ID
|
string |
|
Notes |
notes
|
string |
|
Tabular:
633_transpiration_8955b945a0b49b40794cbd7b304343af.csv
Description: Tres Rios: transpiration. Measurements of leaf-level gas exchange and micro-climate taken using an infrared gas analyzer on individual plant leaves located within study transects at the Tres Rios wetlands. These instantaneous micro-climate and transpiration data are used as inputs into transpiration and evaporation models that scale these data and estimate whole-system atmospheric water losses.
Column |
Description |
Type |
Units |
date_time |
date and time of observation
|
date |
Format: YYYY-MM-DD hh:mm:ss |
obs_num |
Sequential order in which samples were taken on a given day
|
string |
|
transect |
transect ID
|
string |
|
species |
plant species
|
string |
Enumeration:
-
h_umbellate: Hydroctoyle umbellate
-
s_acutus: Schoenoplectus acutus
-
s_acutus_tabernaemontani: Schoenoplectus acutus OR Schoenoplectus tabernaemontani
-
s_americanus: Schoenoplectus americanus
-
s_californicus: Schoenoplectus californicus
-
s_maritimus: Schoenoplectus maritimus
-
s_tabernaemontani: Schoenoplectus tabernaemontani
|
section |
Vertical location along plant where measurement was taken. T = tip of leaf/stem; B = bottom of leaf/stem; integers represent total distance (cm) above water surface.
|
string |
|
photo |
Rate of photosynthesis
|
float |
micromolesPerMeterSquaredPerSecond |
cond |
Conductance to H2O
|
float |
molesPerMeterSquaredPerSecond |
ci |
Intercellular CO2 concentration
|
float |
micromolesPerMole |
trmmol |
Transpiration rate
|
float |
micromolesPerMole |
VpdL |
Vapor pressure deficit based on Leaf temperature
|
float |
kilopascal |
Area |
Area of leaf surface in IRGA chamber head
|
float |
micromolesPerSecond |
stm_rat |
Stomatal ratio estimate
|
float |
dimensionless |
BLCond |
Total boundary layer conductance for the life (includes stomatal ratio)
|
float |
molesPerMeterSquaredPerSecond |
Tair |
Temperature in the sample cell
|
float |
celsius |
Tleaf |
Temperature of the leaf thermocouple
|
float |
celsius |
TBlk |
Temperature of the cooler block
|
float |
celsius |
CO2R |
CO2 concentration inside the reference cell
|
float |
micromolesPerMole |
CO2S |
CO2 concentration inside the sample cell
|
float |
micromolesPerMole |
H2OR |
H2O concentration inside the reference cell
|
float |
micromolesPerMole |
H2OS |
H2O concentration inside the sample cell
|
float |
micromolesPerMole |
RH_R |
Relative humidity in the reference cell
|
float |
dimensionless |
RH_S |
Relative humidity in the sample cell
|
float |
dimensionless |
Flow |
Flow rate to the sample cell
|
float |
micromolesPerSecond |
PARi |
Photosynthetically active radiation as measured by in-chamber sensor
|
float |
micromolesPerMeterSquaredPerSecond |
PARo |
Photosynthetically active radiation as measured by external sensor
|
float |
micromolesPerMeterSquaredPerSecond |
vp_kPa |
Average vapor pressure deficit
|
float |
kilopascal |
VpdA |
Vapor pressure deficit based on air temperature
|
float |
kilopascal |
Tabular:
633_typha_leaves_a72198996370e736e77ae3bb972b1f4e.csv
Description: Tres Rios: indices of primary productivity. Measurements of lenghts of Typha spp. leaves located within study transects at the Tres Rios wetlands. These data are used as inputs into biomass models to calculate above-ground primary productivity
Column |
Description |
Type |
Units |
date |
date of observation
|
date |
Format: YYYY-MM-DD |
transect |
transect ID
|
string |
|
quadrat |
location of quadrat along transect
|
string |
|
species |
plant species
|
string |
Enumeration:
-
s_acutus: Schoenoplectus acutus
-
s_americanus: Schoenoplectus americanus
-
s_californicus: Schoenoplectus californicus
-
s_maritimus: Schoenoplectus maritimus
-
s_tabernaemontani: Schoenoplectus tabernaemontani
-
t_domingensis: Typha domingensis
-
t_latifolia: Typha latifolia
|
plant_id |
plant id (for linking to plant attribute data)
|
string |
|
data_book_ID |
field data book ID
|
string |
|
Notes |
notes
|
string |
|
leaf_num |
leaf ID
|
string |
|
leaf_length |
length of individual plant leaf
|
float |
centimeter |
Tabular:
633_water_quality_0ae1b77ba27e994f9a4719f50d218b40.csv
Description: Tres Rios: water_quality. Measurements of water quality taken in situ and from grab samples collected within study transects at the Tres Rios wetlands.
Column |
Description |
Type |
Units |
date |
date of observation
|
date |
Format: YYYY-MM-DD |
transect |
transect ID
|
string |
|
location |
Location where sample was taken within transect
|
string |
|
tp_mgL |
Total phosphorus concentration
|
float |
milligramsPerLiter |
tn_mgL |
Total nitrogen concentration
|
float |
milligramsPerLiter |
doc_mgL |
Dissolved organic carbon concentration
|
float |
milligramsPerLiter |
tdn_mgL |
Total dissolved nitrogen concentration
|
float |
milligramsPerLiter |
no3_mgL |
nitrate-nitrogen (NO3-N)
|
float |
milligramsPerLiter |
no2_mgL |
nitrite-nitrogen (NO2-N)
|
float |
milligramsPerLiter |
nh4_mgL |
ammonium-nitrogen (NH4-N)
|
float |
milligramsPerLiter |
cl_mgL |
chloride (Cl)
|
float |
milligramsPerLiter |
po4_ugL |
phosphate-phosphorus (PO4-P)
|
float |
microgramsPerLiter |
ph |
pH
|
float |
dimensionless |
temperature_c |
Water temperature
|
float |
celsius |
conductance_us |
Conductance
|
float |
microsiemens |
spec_cond_us |
Specific conductance
|
float |
microsiemensPerCentimeter |
o2_mgL |
Oxygen concentration
|
float |
milligramsPerLiter |
o2_percent |
percent dissolved oxygen saturation
|
float |
dimensionless |