(gentle music begins)
- Arid and semi-arid regions in general
and specifically here in the Sonoran desert,
surface water resources are really scarce
and they're becoming increasingly scarce as we move forward
into the future.
And that's because we have urbanization, we have more people
living here using up these water resources
and we also have changes in precipitation patterns.
(gentle music)
There are artificial sources of water and that's helping
to augment these natural flows.
And in some cases, they're recreating flow in previously
dry portions of rivers and streams.
And that's thanks to treated wastewater discharge.
(gentle music)
Here in the city of Tucson, there are two
water reclamation facilities.
They treat all of our sewage.
And then majority of that water, that treated effluent,
as it's known, is discharged directly into
the Santa Cruz river.
(water flowing)
(gentle music begins)
- We just kinda started going out to the river,
different parts of the river, picking up rocks,
looking at what bugs we saw.
The river is obviously different from all other streams
around your natural streams because it's completely
dependent on treated wastewater or effluent to flow.
So, that's one of the reasons why aquatic ecologists
kind of ignored it in the past 'cause it was seen as
like a second-class ecosystem, one that wasn't as healthy
or as vibrant as other ecosystems.
We knew that there had been wastewater treatment plant
upgrades in the recent years.
So, there was some indication that the health
of the river was improving.
And we just basically set out to see what
that looked like on the ground.
- And we ran into rattlesnakes on the river.
We gone from 115 degrees sampling days in the middle
of the summer where can't keep the sweat
out of our eyes to sampling in the middle of the winter,
where the water is actually quite cold,
really early in the morning.
(gentle music)
- It seems like it will be a chunky one, too.
- Yep.
(sediment clinks in jar)
- Almost immediately we saw some of the strange dynamics
in the river.
One of the prominent ones in that is that the flow varies
with our water use from Tucson.
During the day when people are awake, washing dishes,
using showers, the bathroom, the water levels going into
the treatment plants are high.
So, the treated water coming out of it is also high.
So, the flow is high in the river.
Then at night, everybody goes to sleep except for the people
working at night, very little water gets used
and so the amount of water coming into
the treatment plants is low.
So therefore, the amount of water in the river is low.
So, it has this pretty dramatic cycle from day to night.
(gentle music)
So, we were curious if the operation of the treatment plants
and the water use patterns in Tucson was impacting
or limiting the diversity that we were seeing
in the Santa Cruz.
So that was the initial goal that we set out to study.
- Not a lot is known about these effluent dominated
river systems like here in the Santa Cruz.
So we wanted to look at the aquatic invertebrates
to tell a better picture of what's happening here
in the river.
(ethereal music)
Aquatic invertebrates are the bugs and the insects
and crustaceans that live in the river.
And they're known as bioindicators.
Looking at what's living in the river can tell us
a lot about the overall health of the river.
- And in that early sample, we ended up finding
about 40 species of aquatic invertebrates.
And I think, at that point, probably only 20 or 25
had ever been reported from the river in total.
So that was really an indication that, okay,
this is an unnatural system but it's obviously more diverse
than we've given it credit for largely thanks
to the wastewater treatment plant upgrades in 2013.
(water sloshing)
However, finding 40 species in a river,
even though that was amazing for the Santa Cruz
is not amazing for a natural river ecosystem.
(brooding music)
We've got a little mix of everybody in the labs.
We've got grad students, undergrads and post-docs.
I like to say, as a rule of thumb, for every hour we get
to spend outside playing in the water, we spend eight hours
back in the lab, actually turning those observations
into data.
(equipment clicks)
- So, we collect these aquatic invertebrates samples
from these different sites in the river.
We take 'em back to the laboratory
and we look at 'em under the microscope.
In that process though, we started seeing these brightly
colored objects under the microscope.
(slow rhythmic music)
All sorts of really bright colors reds, whites, greens,
blues, oranges.
Some of them even have sparkles in 'em.
(rhythmic music)
And we realized that we're looking at microplastics
in our sample.
- They really grab your attention and then even some
of the irregular plastics that are broken down
from bigger pieces of plastics, they don't look like
the pieces of wood or minerals and rocks that you get
in your samples.
(lilting music)
- Was never our intention to collect
or start looking at microplastics but inadvertently we are
collecting sometimes large quantities, large concentrations
of these microplastic pieces that are in our local river
system here in the lower Santa Cruz river.
(lilting music)
Any microplastics that go down our drains at home,
here in Tucson, they end up going
to the water reclamation facilities
and with the modern treatment centers that we have now,
wouldn't be uncommon to have 95% removal rate
of these microplastics prior to the treated effluent
that's discharged into the environment.
But because the concentrations of microplastics
are so enormous, even 5% that's leftover can still represent
a large amount of microplastics, especially over time,
as it all adds up.
(gentle music)
We have those microfibers that are going down the drains
when we wash our clothes, we have potentially
microplastic beads in personal care products
that go down our sinks, in our shower drains
and they end up going to the river.
(gentle music)
But then you also have litter out on the landscape,
especially when it comes to single use plastics.
So, you have cups and lids and straws and plastic bottles
and plastic bags, for example.
If they're not disposed of properly, if they're not recycled
properly, if they're littered out on the landscape,
eventually those make their way down gradiant
from wind and rain water runoff into our river
and stream systems.
(brooding music)
And so they go from maybe a plastic bottle to thousands,
maybe hundreds of thousands of small plastic pieces,
as they break down over time and then they can spread
even more easily into the environment
and get into the sediment and into the rivers and streams.
(gentle music)
- To us, the amount of plastics seemed extreme
when we were looking at those initial samples.
But when we compare the amount of plastics that other
researchers are finding in other rivers,
the Santa Cruz really isn't all that high,
especially considering that none of its flow
during non-rainy times is natural, right?
So, a hundred percent of that flow is coming
from the treatment plant.
And we know that the treatment plan water
has plastics in it.
And yet what we see in the Santa Cruz plastic wise
is pretty similar to what you'd see in a river
that's 80 or 90% natural flow and only has a small
contribution from a wastewater treatment plant.
(water flowing)
- These artificial stream systems, like the Santa Cruz river
that are supported by effluent are the future.
The surface water resources that are incredibly important
to the biodiversity, not just the things that
live in the water themselves, not just the fish
and the aquatic insects but they're important
for the larger ecosystems, as a whole.
So all the mammals, the birds, the plants, the trees,
the riparian habitat, it's because of that it's important
to study these systems from scientific research perspective
but also from environmental managers.
- We need to get the data to show the real value
of putting this water in these washes
and these dry river beds.
So that five or 10 years from now, when the price
of that effluent is up and the demand is up that we can say,
you know, this is why we need it in the ecosystem.
This is why we need it in the river bed.
If we don't make the economic argument for the value
of this ecosystem, the value of these affluent dependent
rivers, then some competing use will win.
And they'll take that water out of the river.