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Jody Eimers: I understand that you returned
to a subject that you were active in doing

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research in the 70s and 80s on trends.

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So can you explain the importance of that
work?

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Bob Hirsch: Sure.

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I’m always delighted to talk about that
subject, and I’ll talk about it a little

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bit by talking history.

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Back in the early 1970s, the USGS was beginning
to think about these issues of water quality

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and how it changes over time.

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To help understand are things getting better,
are things getting worse, where is that happening,

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etc, and we were beginning to collect systematic
records of water quality in our Nation’s

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rivers.

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But we hadn’t really thought about the question
of what’s a valid way of analyzing those

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records to see whether things are really getting
better or worse because water quality in a

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river is very much influenced by a set of
natural processes and very much influenced

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by high flow events, drought years.

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It’s very much influenced by the changing
of the seasons, so there’s a lot of variability,

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which is just very natural and very normal.

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And what we’re looking for are the long-term
changes from that general pattern we see over

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time.

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So I was asked early in my career to develop
some methodologies for getting at this question

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of trends in water quality.

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Well, at the time we were doing it, the records
we had were five or six or seven or eight

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years long.

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And we had to develop some very simple repeatable
kinds of methods for doing that, and we were

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successful in doing that.

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And a lot of those methods are used through
the USGS, in fact, throughout the world as

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ways of analyzing trends.

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Well, then I left that kind of research and
moved into management but always keeping an

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eye on what was going on in that field.

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And as time has progressed, we’re now looking
at very good consistent long-term water quality

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records that are 20, 30, 35, 40 years long.

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They may have 700 or 800 observations in them
of the chemistry of a particular river.

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What I saw was we needed a new set of tools
to really get at an understanding of the kinds

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of changes that are taking place.

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For example, one of the things that we now
see is the particular degradation of the quality

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of water at low flow, which is probably associated
with the pollution of groundwater coming into

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the river at low flow while we may not be
seeing a change in water quality at the higher

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flows.

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The nation is putting a lot of emphasis on
controlling non-point source pollution, and

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a lot of people want to know are we making
progress or not, and we really needed a set

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of techniques to do that.

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So I’ve been working with collaborators
in USGS offices around the country working

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on understanding the changes in places like
here, the tributaries to Chesapeake Bay, the

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Mississippi River, Lake Champlain and probably
other areas in the future.

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I’m also looking at trends associated with
just things about river flow itself to help

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us get at the question of are the size of
floods changing potentially because of greenhouse

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gas driven climate change, our droughts changing,
and how do we tease that information out of

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the datasets to look through a lot of natural
kind of noise to see if there is a signal

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of what humans are doing to change our Nation’s
rivers.

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[End of Audio]

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Duration: 5 minutes

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1
A Conversation with Bob Hirsch- Water-Quality

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Trends
Jody Eimers, Bob Hirsch

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1
Filename

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Speakers’ Names

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_____________________________________________________________________________________

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www.gmrtranscription.com