Jody Eimers: I understand that you returned to a subject that you were active in doing
research in the 70s and 80s on trends.
So can you explain the importance of that work?
Bob Hirsch: Sure.
I’m always delighted to talk about that subject, and I’ll talk about it a little
bit by talking history.
Back in the early 1970s, the USGS was beginning to think about these issues of water quality
and how it changes over time.
To help understand are things getting better, are things getting worse, where is that happening,
etc, and we were beginning to collect systematic records of water quality in our Nation’s
rivers.
But we hadn’t really thought about the question of what’s a valid way of analyzing those
records to see whether things are really getting better or worse because water quality in a
river is very much influenced by a set of natural processes and very much influenced
by high flow events, drought years.
It’s very much influenced by the changing of the seasons, so there’s a lot of variability,
which is just very natural and very normal.
And what we’re looking for are the long-term changes from that general pattern we see over
time.
So I was asked early in my career to develop some methodologies for getting at this question
of trends in water quality.
Well, at the time we were doing it, the records we had were five or six or seven or eight
years long.
And we had to develop some very simple repeatable kinds of methods for doing that, and we were
successful in doing that.
And a lot of those methods are used through the USGS, in fact, throughout the world as
ways of analyzing trends.
Well, then I left that kind of research and moved into management but always keeping an
eye on what was going on in that field.
And as time has progressed, we’re now looking at very good consistent long-term water quality
records that are 20, 30, 35, 40 years long.
They may have 700 or 800 observations in them of the chemistry of a particular river.
What I saw was we needed a new set of tools to really get at an understanding of the kinds
of changes that are taking place.
For example, one of the things that we now see is the particular degradation of the quality
of water at low flow, which is probably associated with the pollution of groundwater coming into
the river at low flow while we may not be seeing a change in water quality at the higher
flows.
The nation is putting a lot of emphasis on controlling non-point source pollution, and
a lot of people want to know are we making progress or not, and we really needed a set
of techniques to do that.
So I’ve been working with collaborators in USGS offices around the country working
on understanding the changes in places like here, the tributaries to Chesapeake Bay, the
Mississippi River, Lake Champlain and probably other areas in the future.
I’m also looking at trends associated with just things about river flow itself to help
us get at the question of are the size of floods changing potentially because of greenhouse
gas driven climate change, our droughts changing, and how do we tease that information out of
the datasets to look through a lot of natural kind of noise to see if there is a signal
of what humans are doing to change our Nation’s rivers.
[End of Audio]
Duration: 5 minutes
1 A Conversation with Bob Hirsch- Water-Quality
Trends Jody Eimers, Bob Hirsch
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