"The following is a recording of the USGS Congressional Briefing on the
Impacts of Climate Change on Water Resources given on April 27, 2007 at
the Rayburn House Building in Washington D.C."

**Bob Hirsch:** "Good morning and welcome. Does this sound OK people?
Sounds a little funny from up here. I'm Bob Hirsch, I'm the Associate
Director for Water at the U.S. Geological Survey. And I'm pleased to be
here this morning and I'd like to thank our Congressional sponsors for
this event. Senator Jeff Bingaman, Senator Lisa Murkowski, Congressman
Jim Moran, Congressman Earl Blumenauer and Congressman Wayne Gilchrest.
We want to thank them for allowing us, the USGS, to present this
briefing today on the impacts of climate change on water resources. I
want to give special thanks to the Interstate Council on Water Policy
who is our host for today's event and I want to introduce to you Peter
Evans, Director of the ICWP, who's been a very strong supporter of water
data and water science through his role as Executive Director of ICWP.
So, Peter if you'll come up make a few remarks about ICWP."

**Peter**: "Glad to thank you Bob and it's a pleasure for me to be here.
My name's Peter Evans and I'm the Director of the Interstate Council.
We're an organization that represents state and interstate water
officials. One of our top priorities is to nourish the water data and
science programs that water managers need in order to make intelligent
decisions about both land use and water resource management in the
future.

The other top priority that we have has been to nourish interstate
organizations that state officials have organized where water resources
cross state lines. And so, we've got a poster that will tell you more
about the organization and there is some literature here. I just want to
say, you know, we really appreciate the opportunity to support the USGS
in this.

We always learn a lot from the GS and of course I want to point out that
what we're going to talk about climate change and focus on western
states. Climate issues are huge concerns in the eastern states as well.
As you probably notice in the last couple of days with the forest fires
and the extension of outdoor water restrictions in Georgia, but it's
also affecting Florida and Alabama very seriously right now, so, thank
you very much."

**Bob Hirsch**: "Thank you. Thank you Peter. I'd like to just say a
little bit by way of introduction about what is the USGS role in this
topic of water resources and climate change and I'd just like to walk
through very quickly some of the ways that we are involved. We've
formally had a global change science program for a decade and a-half and
it's a very vibrant and active program and you'll get to hear, I think
some important results of that program in a few minutes.

One of our most important roles in this area is in the continuing
collection of hydrologic data, data on ground water levels and data on
stream flow and we have records of this stretched back as much as 120
years. But it isn't enough just to simply collect that data, it's also
very important to analyze it and that's something we're very much
engaged in looking at these long records for the kinds of things that
they can tell about how the climate is changing and how those climate
changes affect stream flow. And we particularly find some very
interesting results in parts of the country that are significantly
affected by snow and there are real changes there and our first speaker
will talk about that.

Another aspect of our climate change program is participation in global
and regional climate modeling efforts to really help provide the land
surface to atmosphere interaction components to those and our first
speaker, Chris Milly, has an example of that in the way he has worked so
closely with the modelers at NOAA's Geophysical Fluid Dynamics Lab to
bring that land component to their modeling efforts.

We also do extensive studies, relating to the interface between the
oceans and fresh water both in terms of surface water and what happens
in estuaries, as well as what happens in ground water and clearly with
the sea level rise, this issue of ocean to fresh water, interactions is
crucial.

And finally, we work with many, many water management agencies through
our cooperative water program. Many of whom have major responsibilities
for managing water supplies, water resources and our trying to come to
grips with how to deal with and how to think about the climate change
and a long term climate variability. We also work closely with our
federal partners such as the Corp of Engineers and Bureau of Reclamation
and National Weather Service in their roles as well.

So, I just wanted to give a flavor of some the kinds of ways that we, at
the USGS are involved in this issue. We\'re going to have three speakers
this morning, one from the USGS and then two from the west, from other
agencies with other experiences relating to water resources. Our first
speaker is going... and I would ask her we hold questions until we get
all the way through all of the talks and then we'll, we have just timed
it so there should be an adequate amount of time to ask questions of all
of our speakers.

First, we have USGS Research Hydrologist, Dr. Chris Milly, who will set
the stage for what we know about the potential impacts of climate change
on water resources globally and the current situation as we know it in
the USGS. As I mentioned, Chris is stationed at NOAA's Geophysical Fluid
Dynamics Lab in Princeton New Jersey. His research focuses on
understanding the global water cycle and its connection to climate and
vegetation. He has made pioneering contributions to the problem of
detection of climate-driven changes and stream flows, flood risks and
water availability and he has designed the land component of GFDLs
numerical climate and earth system models. And so, Chris really will
help us, I think set the stage for this discussion. So, Chris Milly."

**Chris Milly**: "Good morning. Climate is changing and climate change
is having impacts on the waters of the United States. Next slide please.
These are the questions and to boil them down, there's really two
questions. One is, what the heck is going on? And then the bottom two
questions can be boiled down to what are we going to do about it. Next
please. I'm going to focus on the what's going on question in terms of
three issues: Sea level rise, snow pack loss, and the geographical
re-distribution of water resources. Next.

We're going to start with sea level rise. Next. In the last century, sea
level rose about six inches. In the last decade of the last century that
rise rate accelerated to about a foot per century and projections for
the coming century are for anywhere from a half a foot to 2 feet of sea
level rise. That's where most of the estimates fall. Next. What are the
consequences of sea level rise specifically for water supply, the main
consequence is increased risk of salt water contamination of coastal
water supplies, whether they be derived from surface water sources or
ground water resources. One of other speakers is going to develop this
concept a little more detailed so I'm going to move right on to my
second issue. Next please. Which is that of snow pack loss. Next.

We're going to focus on California because that is where we expect the
largest, earliest manifestations of snow pack loss. We're going to look
at a USGS streamgage site on the Merced River up in the Sierra Nevada.
This is the gauge at Happy Isles Bridge. Next please. The Sierra Nevada
and California get their precipitation in the form of snow, mainly and
much of it falls in the Sierra Nevada where it forms the snow pack in
winter. Next slide.

In the spring time, the air starts warming, the sun is higher in the sky
and we have snow melt. That drives run-off into the rivers, which come
down into the Central Valley. And on average, it takes about four months
from the time that, that water falls as snow until it comes down out of
the hills to the valley as run-off. Next slide please. That water is
coming just in time. That four-month delay is a great thing because late
spring, early summer is when agriculture is spinning up, you're
irrigating your fields, getting ready for the growing season and also
the seasonal demand from urban populations is spinning up around then
too. So this, this delay of the run-off by the snow pack is a great
thing.

What's been happening in recent years and has projected to continue as
we go forward is an increasing amount of precipitation is falling not as
snow as rainfall instead. Next slide. So the consequences of this loss
of snow pack are really the loss of some environmental services that the
snow pack provides and I'll mention three of them.

One is the loss of a natural flood control system because when
precipitation arrives as rain, it's much easier to produce a flood than
when it comes down the hills as snow melt. Secondly, we have a loss of
that reservoir that time delay mechanism that helps us to balance the
seasonal supply and demand for water in California. And finally as the
snow pack dries out, melts earlier in the year or the mountain
environment dries out earlier in the year and in general, the tendencies
toward increased risk for fire, so we lose that fire suppression effect
of the snow pack. Next please.

We're moving along here. I'm going to focus most on this third issue and
this is an issue that I think has received the least attention, but has
potential to have some of the greatest impacts in the long run and
that's why I'm going to spend a little extra time on it. Next please.
And in fact, before I show you any model projections, I'm going to the
question that half of you probably would shoot your hands up and ask
anyway, which is why should we believe these models? Is there any
credibility to them? And so I'm going to spend a good digression here
addressing that question. Next please.

So we've gone and collected stream flow data including USGS but from
National Hydrologic Services around the world and analyzed those data to
try to put together a picture of one of the regional patterns of ups and
downs during the 20^th^ century in stream flow and hence, in water
availability. Where did it get wetter, the blue circles. Where did it
get dryer, the red circles. And the long term trends and we all know
there\'s plenty of ups and downs, but there's some long term trends.
Those have a component of natural variability, but there's a hypothesis
that they also have a component that's driven by changes in climate
forcing mechanisms. Be they natural or anthropogenic.

What we did was to basically go to the climate modelers and say, you
know, if you're so smart, if you can tell what's going to happen in the
21^st^ century, prove it, you know, go back to 20^th^ century. We're
going to tell you what we got from our stream flow analysis, but you
tell us out of your models what the run-off changes are. We'll analyze
that, turn it into stream flows and make a similar comparison to what we
did with the obs. So that's the comparison I'm going to show you. Next
slide please.

On the top, it began as the observations, on the bottom, I'm going to
show you what picture the models taken together and sort of a boiled
down into a single result. What they projected retrospectively for the
20^th^ century. Now, what's making things change in the 20^th^ century
in the climate model? What's making things change is the changes in CO2
that are put into the model that changes the volcanic eruptions and so
forth. Things that we know happened that affect climate. Solar
variability, it's in there. All of those natural effects and
anthropogenic effects are in the models. Tell the climate modelers,
okay, what's your picture? And I'm going to reveal that picture now.
First slide.

South America, and we're going to work our way around the globe here
clockwise. So let's go to the next one North America and on to Euroasia,
Europe and Asia and finally to Africa and Australia.

There's a pretty good agreement between those two pictures subjectively.
What about objectively, what can we say? Well, there's a lot of dull and
boring statistics, technical analysis we can do, but I'd like to boil
down all the results of that into one basic statement, which is that the
degree of agreement between these two maps is substantially larger than
could possibly have occurred by chance. It is indicative of skill. It is
indicative of ability of the models to give us information about
hydroclimatic change, about water availability change. We're moving
beyond temperature. We're talking about water.

I don't want to, you know, overdo this. Models are not perfect. Models
are far from perfect. They need a lot more work. The glass is not empty,
but neither is the glass full. Okay. I don't know how full it is. It's
somewhere in between. And whatever is in that glass, I think it's
useful. It's useful for water managers can help satisfy their thirst for
information about water. Information they need to manage that resource.
Next slide please.

So, given that background, I've asserted that climate models have some
skill and now I may put up for you a picture that shows the projections
of those models for about the middle of this century, 2050. The picture
is colored in many places. Where it's not colored, it points where the
models were less, had a lower degree of agreement. Basically, we use 12
different climate models. If 8 or more of them agreed, we went ahead and
colored a country or a state. If 11 or 12 of them agreed, we put some
diagonal hatching in there, okay. The colors give you the amounts 5%,
10%, 20%, 40% changes. Oranges and browns are decreases. The blues are
increases.

Where are the drying spots? Northeastern, South America, southern
Africa, southeast Australia. The Amazon region, I'm sorry the, ah, don't
quote me on that. The Mediterranean region that's northern Africa,
southern Europe, the Middle East and on eastward. And finally, and let's
go to the next slide for a zoom in on the USA averages by state.
Finally, the western mountain region and in particular the southwest.
Increase is 20% to 40%, 10% to 20%, I'm sorry decreases in water
availability. And in Alaska, a great big whopping increase that's robust
across the models. Next slide please.

Yeah, what are the consequences of these projections for practical
matters for water availability? Here are three of them. The first is the
most obvious. There's a changing risk in the southwest, that's an
increasing risk of probability of failing to meet water demands,
decreasing probability of failure in the Midwest. There's always an up
and a down. The second point here is changing risk of floods, probably a
tendency toward increased risk of floods in the Midwest, decreased risk
in the southwest. Although, we're just talking about that geographical
redistribution issue here, you got on top of that the loss of snow pack
and that's going to cut the other way in the west. And then changing
risk of droughts, which is one of serious concerns for the southwest and
the mountain west. Next please.

So, I come back to this slide I showed early on. I've talked about
what's going on the first two slides and now I want to talk briefly
before I finish here about what we can do about it and specifically what
can science contribute to society's decisions about what we do about it.
Next please. The two big buzz words in what we're going to do about it
are mitigation and adaptation. Mitigation means doing all the things you
hear about, you know, getting rid of your SUV and then power plants, all
that business. All those things that are trying to avoid climate change.
The message which I try to boil down in this picture is that mitigation
can have their enormous effect on potential impacts in the latter half
of the 21^st^ century. But there are some time delays just built in to a
number of systems which mean that we can only make a dent by means of
mitigation in the first half of this century. What does that leave? That
leaves the other buzz word adaptation.

Adaptation means, climate change is in the pipeline, it's real, deal
with it. It's unavoidable. So adaptation is what we want to focus on and
it's going to be a major customer, I think, for science information
about water. Next slide please.

You know, you can list all the possible things from which water users
can decide on how they may adapt, and I won't read them off the slide
here. But the main point I want to make is that, these are decisions
that I don't make, the USGS doesn't make, the public makes these
decisions and they need information in order to make those decisions.
Next please.

When we talk about information, we got to keep in mind this real dilemma
that is being faced by all of us and that is there's always value in
making a decision as soon as possible in order to minimize effects of
the change, but on the other hand, the knowledge phase is evolving
really rapidly. So you feel like, I, I just like to wait until tomorrow
or next year to make this decision. And I think every decision, you have
to balance the value of waiting and you know, there's no simple solution
to that. Fortunately, citizens in general, and water managers in
particular are no strangers to the practice of making decisions under
uncertainty, but they just need that information. Next please.

So, this is my final slide. What are some of the things that we can do?
What kinds of information can we provide? We can identify and quantify
the vulnerabilities and in fact, that's sort of what I've been trying to
do in the first part of this talk. Moving forward though, we need a lot
more detail in the pictures and that's why we will continue with the
kinds of work that we do, monitoring the environment, trying to model
that and doing research so that we can build the models and put all that
together into an understandable picture.

And then on top of that, and not just to tack on, something we've got to
really internalize as part of the process is communication. We need to
greatly crank up the rate of communication because things are changing
and they're changing quickly and our knowledge of them is changing
quickly. So I used the analogy, the metaphor, before of a glass of
water. And you know, one could argue, some people would argue that yeah,
we've got some water, but, you know, it's even worse than that we don't
have the glass to deliver it to the thirsty water manager. We're
delivering it with an eyedropper. What we need to do is think real hard
about how can we very efficiently and very quickly get information
through the system from the basic science right through to the water
user. And with that I'll close my remarks and as Bob mentioned, we'll be
taking questions later. Thank you."

(Applause)

**Bob Hirsch:** "Thanks Chris. Our second speaker is Kathy Jacobs,
Executive Director of the Arizona Water Institute. The Arizona Water
Institute is a consortium of three Arizona universities focused on
water-related research, education and technology transfer related to
water supply sustainability. Kathy is also Deputy Director of the NSF
Center for Sustainability of Arid Region Hydrology and Riparian Areas
and a professor in the University of Arizona Soil, Water and
Environmental Science Department. She has more than 20 years of
experience as a water manager in the state of Arizona. Her research
interests include ground water management, water policy, connecting
science and decision makers, stakeholder engagement and the use of
climate change and climate variability information for water management
applications. She has served on five National Academy panels and wrote
the Water Sector chapter for the U.S. National Assessment of the Impacts
of Climate Change. Dr. Kathy Jacobs."

**Dr. Kathy Jacobs:** "Good morning. I'd like to thank the United States
Geological Survey for inviting me to join you here today and share a
little bit of information about the prospective of water managers in the
southwest related to climate change. And I think the main message what
was previously essentially a background issue has now become a primary
concern for water managers and there's a real need for improved
scientific information so the water managers can do the kinds of
adaptation that Chris was talking about. Next.

I represent the Arizona Water Institute, which exists specifically to
help move information from the university system into the water
management arena and to share it with various communities, tribal
entities, watershed groups, government entities that are actually having
to make resource management decisions. This entity essentially builds
the bridge between the research faculty and the scientific community and
those who actually make decisions. We have 400 water-related experts in
the University of Arizona, Arizona State University and Northern Arizona
University. Those folks are now being essentially redirected towards
actually applying their knowledge to sustainability issues. Next.

Among the folks who are in the University of Arizona and other folks who
actually work for the United States Geological Survey are experts who
work with tree ring information. And what these people do is actually
take the width of the tree rings and reconstruct what past history of
water supply looks like on that basis. So they were able to say what the
stream flow looked like well before you were able to gauge water flow in
streams.

What you see here are two different chronologies that are reconstructed
from these seen on the Colorado River. And they both tell us something
very dramatic that we would not have understood if we didn't have this
long term perspective. This is extremely important to understand that
what we are actually observing today is not typical of what we've seen
in the past. We can't tell that unless we have good data about what
happened historically.

In the top graph, you can see a reconstruction that shows a big peak in
the early 1920s. That happens to be the time when the Colorado River was
allocated between all the basin states. Guess what happened, they
allocated more water than actually exists in the river. This is sort of
the baseline that we're operating from at this point. In the second
graph, what you see is actually a very long chronology. This is actually
one of the longest ones I've seen more than 1,000 years. We've been
adding hundreds of years to these chronologies. And what this one tells
us is there are actually historic droughts that far exceed especially in
length the types of droughts that we've experienced in this century. So
what we're saying is that even in the absence of climate change, there's
an extreme amount of variability, but its not just variability on an
annual basis, it's long term variability and we have not actually
observed the kinds of shortages that were typical even in a natural
state. Next.

When we lay over the implications of climate change on top of this
historic variability, we are actually adding significant risk to our
water supplies and the reason that that is a problem is that as the
temperatures increase, the impacts particularly from drought become much
more substantial. It's important for water managers to realize and many
of them still do not, that the past is not an analogue for the future.
We have always designed our infrastructure based on the past 30 years or
the past 50 years. We need to understand that that past is not what the
future is going to like anymore and to the extent that we do understand
the droughts of the past, the ones in the future are likely to be more
extreme.

Secondly, there's this issue of stationarity and I, as a water manager,
historically did not understand that when the climate that we were
observing was not essentially oscillating around the mean. It wasn't
just going up and down around a straight line. What it was doing is
exhibiting long term trends, wet trends, dry trends. And there are
periods in the record that actually go for decades where a specific type
of climate essentially get stuck. Now, what we're seeing is some long
term trends that may actually continue into the future and we don't know
where they're taking us, but it's not even going to be the kinds of
trends that we saw in the past more than likely. Understanding this lack
of stationarity in the system is really important for water managers and
the only way you could do that is by understanding the science. Next.

We're looking at the Colorado River, where incredibly, it's very
important for us to understand how important that river is to the water
supply of the west. There's 25 to 30 million people served by that
river, 3-1/2 million acres of farmland, climate change impacts on these
flows are projected to be between 10% and 40%. Remember, this is an
overallocated river to start with.

The temperature implications are part of the problem here. Temperature
actually drives both the demand up and the supply down due to
evaporation, etc. And you've heard about that from Chris. We've been
seeing in flows into Lake Powell that are actually below of what we
previously considered normal, 7 out of the last 8 years. We may need to
reconsider what is normal. And clearly the western states are getting
this issue. They're working on shortage sharing for the first time.
We've never had a shortage, we're heading for a shortage. Next.

And of course, a lot of what\'s driving all this is not just that we've
got a shrinking supply situation, we have a really significant increase
in demand associated particularly with municipal development, but also
associated with changing values. The need to protect the environment,
endangered species, etc...major concerns about multidecadal drought
overlaying the situation. Next.

So, what we're actually thinking in terms of vulnerability is that
habitat-ecosystems are among the most the things we need to be most
concerned about. The central Arizona project which delivers a
significant portion of Arizona's water supply has the lowest priority of
any of the water projects on the Colorado River. So Arizona is
essentially the center of impacts. And as you saw on Chris' slide, it's
one of those states where the run-off reductions are anticipated to be
greatest. We've got to be among the highest rates of growth. It's a
substantial problem and it's in the context of multiple other states
that are all vying for that same water supply from Colorado River. Next.

So, what do we need to do about this? There are many things we can do
and I've been focusing a lot of my energy. I'm trying to help people
understand what we can do in the short terms, do the adapting that Chris
talked about. First of all adaptation requires better information. And
adaptive management, per se, requires real time information and constant
assessment of whether or not we're doing a better job. It's very
expensive and it requires that we actually focus our efforts on the
critical or vulnerable systems and we know where they are. We don't have
the resources to do this sort of a blanket. But we absolutely do need to
invest in monitoring. Next.

We also need to take better care of our ground water aquifers. In
Arizona, we're using them essentially as our storage for years when the
Colorado River is in short supply. We are using those aquifers
essentially as our reservoir system. There are impacts associated with
using the aquifers that way. And to the extent that they are not
replenished on an annual basis we are actually dewatering these
aquifers. And what's happening across the whole country is that as
surface becomes more short, we focus more on groundwater use. And that
overuse of groundwater is generally not regulated. It is, to some degree
in Arizona, but we have not done an adequate job of protecting our
aquifers, or studying them, or looking with the long term trends from
the scientific perspective are. Next.

Another adaptation, which of course is the first one that comes to most
water managers\' minds, is the very large set of engineering solutions.
And I don't want to in any way denigrate how important these solutions
are and I'm not even going to go through them all because it's quite
obvious that there are multiple ways of enhancing supply through
technology. But we also need to recognize that a lot of this isn't about
engineering. It's about understanding the science of the system,
understanding what the future extremes could be and that we're not going
to be seeing the same things we've seen in the past. We could see abrupt
changes in the planet that we haven't seen before and we need to connect
energy and water because if we don't take that as an integrated whole,
we're going to miss a significant part of that picture. It takes a lot
of energy to pump water. It takes a lot of water to pump energy. And we
can't treat these as separate systems. Next.

We also need to do a better job of using climate information where there
are multiple tools emerging and many ways of connecting climate
information to water management, there's not enough folks actually
understanding what the benefits of all this are. And the outcomes are
probabilistic, they're not certain. However, they're very useful and we
need to invest in this. Next.

We also need to invest generally in decisions support. We need to make
sure people understand that there are decisions that are being made
today about our water supply infrastructure that have very long term
implications. The things that they are doing or not doing today are
actually increasing risk in the future, so getting that decision support
to them as quickly as possible, getting scientific information that is
usable and understandable and timely into water managers\' hands is a
really important contribution that the USGS and others need to make. It
is going to cost money. We are going to need to invest in this. If we
don't invest in this, the overall costs in society are going to be much
higher. This is essentially an insurance policy. Next.

And finally, I just want to emphasize the fact that this is no longer a
question for water managers. They have actually generally crossed the
threshold. They believe that climate change is happening. They are
receptive to new information and they want to know what it is that they
should do about it. And I'm here to encourage you to focus on not just
mitigation or admission strategies, but actual investments in
adaptation. Thank you."

(Applause)

**Bob Hirsch**: "Thank you Kathy. Our final speaker is Curt Schmutte,
Principal Engineer and Water Manager of the Metropolitan Water District
of Southern California. Curt previously worked for the California
Department of Water Resources for 21 years, where he led multiple
programs and projects involving the Sacramento, San Joaquin, River Delta
and Suisun Marsh including levee improvement programs, land subsidence
research, risk analysis, dredging material reuse projects, water quality
studies and wetland restoration projects. Since joining the Metropolitan
Water District of Southern California last May, he has been analyzing
seismic flood risk mitigation, strategies and large scale ecosystem
enhancements. Curt Schmutte."

**Curt Schmutte:** "Thanks Bob. And thank you to the USGS for this
opportunity to talk about California and the California Bay-Delta
System. What I'm going to do in the next 10 minutes is give you a quick
overview and background of the Delta and then briefly talk about
somewhat the principal drivers of change, some of the key risk that are
affecting our Bay-Delta System. And then I'm going to conclude by
talking about some of the critical research on investigations that the
USGS is doing to help solve some of the very, very important problems.
Next.

California has a 1.5-trillion dollar economy and that if California were
a nation that would be about the 6^th^ largest economy in the world, so
we have a very important economy. The Central Valley is where about half
of the drainage in the state falls and all of that drainage drains out
through narrow opening of Carquinez Straits.

The Central Valley is also the home for much of the fruits and
vegetables that we all enjoy across the country, so it's a very
important place. Chris touched upon this point, but I\'ll reinforce it,
that is, in California, we have a spatial and temporal problem. That is,
unlike other parts of the country, most of our precipitation falls in
the winter months and falls in the northern third of the state or 80% of
the total rainfall or total precipitation in the north. Our demands are
in the dry years, during the dry parts of the year and are in the
southern two-thirds, in the Bay Area and southern part of the state. So
we have to store and move vast quantities of water and the delta is in
the heart of that movement across the state of California. Next.

So let's take a closer look at our Bay-Delta System. Briefly, a little
bit of facts about the Delta. Delta is 60 islands, 700,000 acres, 1100
miles of levees and about 700 miles of channels that make up this
system. I'm going to give you a quick overview of what if you were
flying or looking around the Delta and what it would look like. So this
is kind of a temporal view of the Central Delta, you don't see a lot of
vegetation beyond these loggings here, baron and a lot of farmland. And
that has consequences and we shall talk about it in just a minute. Next.

Standing on top of a levee looking down at the farmland, highly organic
soils, big consequences. Next.

One of the few remaining wetlands in the western part of the Delta and
the eastern of the Suisun Marsh. Next.

If you were traveling 200 years ago in the Delta, this is probably what
you would have seen most of. Very little of this left today, this
riparian forests, most of the vegetation has been removed. Next.

And 200 years ago, if you were looking across the landscape then journey
tidal marsh, riparian forest in the background. Next.

So how it is, we have this vital 1.5-trillion dollar economy and most of
the rainfall and precip is north and the demands are south, it is this
water highway that gives water to the California economy. Next. So,
next.

Two-thirds of the state's residence some 23 million people get some or
all of their water from this system right here. 3 million Bay Area
residence get a third of their water from the Bay-Delta, southern
California. Next.

There are 55 fish, 221 birds, 45 mammals, 16 reptiles and 10% of the
remaining wetlands reside in this estuary system. And when I say
Bay-Delta, what I'm really talking about is that San Francisco Bay,
Suisun Bay and the Sacramento-San Joaquin River Delta. Next. So, where
does that water go? And where the people that use it? Again the Bay Area
gets 33%, Kern County 23%, southern California gets 30% of their total
water supplies through that Delta System. Next.

One of the... Now, I'm going to talk about these principle drivers of
change, the key risk that we face. The Delta at one time was all at sea
level. Today, we have some areas that are 20, 30 feet below sea level.
We call, I called them earlier islands, 60 islands. See, everybody
thinks of an island as something that sticks out above the water? Not
here. In the Delta our islands are really holes and, next slide. So,
originally, about 200 years ago, if you round the Delta, the islands
were originally like that. Now, they're bowls, like a teacup surrounded
by water that's essentially at sea level and the reason that's happened
is because the farming and farming has taken basically oxidized, that
is, taking carbon in the soil of these organically rich soils and
converted that carbon into carbon dioxide. And so we have measured, the
USGS has measured 50 pounds per acre per day of CO2 coming off these
farmlands and so we're losing historically as much as 6 inches a year of
land surface elevation, that's currently about 1-1/2 to 2 inches a year
of land surface dropping. So we now have lands, as I said 20 to 30 feet
below sea level, holes or carbon holes. Next.

So, let's take a closer look at another driver of change and the one
that we're talking about here today and that's sea level rise. This view
of the Central Valley looking from the Pacific Ocean through the San
Francisco Bay, Suisun Marsh and the Delta, and let's take a closer look
at sea level rise. Next.

One of the things that the USGS is playing an integral part in is
discovering, identifying and helping to understand what are the
consequences of a foot, 2 feet, 3 feet, 4 feet of sea level rise on this
vital system that we have in California. One of the things that's going
to happen is we know the depth is going to increase and that's going to
cause further sowing improvement. The shoreline will likely increase.
One of the things that I didn't expect that we're finding out is that
the tide will actually amplify. One of the things that happens in a
estuary like this is there is a resonance that occurs as the tidal wave
moves into the system, it reflects off the sides and if we are seeing a
couple of feet of sea level rise, we could likely see a tidal
amplification, meaning that the tidal range not only increases with
higher sea level but we're seeing an amplification beyond that. Next.

And we could see flooding of Delta islands. So we also have the third
driver of change, which are seismic events. I call them the triple S's,
subsidence, sea level rise and seismic. And now I'm going to show a
quick reanimation of, if you combine all these risks the kind of thing
is possible when you have ongoing sea level rise, ongoing subsidence and
a seismic event, so what we're going to see here is actually beyond the
springs so we're going to have some help over here. There you go.

We've actually had a seismic event. The earthquake 6.5 and we had some
levees that are liquefying. And now, as those levees began to liquefy
and slum, some of them are overtopped and those red dots were
representing islands therefore sustaining levee overtopping. So as we
pull away here, you're going to see some 20 holes in the delta that are
beginning to fill up with fresh water. We quickly ran out of the fresh
water in the system, and the only place to fill, about 2 million acre
feet of void that's below sea level is from the San Francisco Bay and
Pacific Ocean.

And so what you'll see in just a minute as we quickly jump over. Now
we're in the very first minutes and hours of this event occurring. And
the islands are beginning to fill up of mad rush of water, 20 ft/sec
velocity at some of these channels as the water is rushing in to fill
these holes that are below sea level. If you pay attention to the far
left in the screen and you'll see this is the ocean now starting to rush
in into the Bay-Delta System. And remember from that slide before, that
this is the California Water Highway we're looking at. This is how water
gets from northern California to these big pumps down here in the
southern part. And we're now accelerating this animation so that we're
actually going through tidal cycles. You can see the tide popping in and
out. But the delta has essentially become the San Pablo Bay in terms of
its salinity levels. Okay, next.

So this, what you just saw was not an easy thing to do. Obviously, there
were some photography here or some animation sophistication, but the
actual science and hydrodynamics that went into understanding this was
not possible 5 years ago. It's only through complex hydrodynamic
2-dimensional, 3-dimensional modeling and the work that USGS has done in
terms of understanding that bathymetry and understanding things like
gravitational circulation that we've been able to better understand that
system and be able to plan for it. So, they've been able, through their
work contributed in these key areas. Next.

Here's the Suisun Bay and on the bottom you get the sense of the
bathymetry variability in the system and its that bathymetry unlike many
other estuaries, it is the key driver in understanding how the salt is
going to mix in the system. Next.

And finally, I'm going to conclude by talking about that third driver of
change, subsidence. I call it the silent killer, it's often
underappreciated because it's the type of thing that's going on
everyday, slowly, we're losing carbon to the atmosphere as CO2 and these
islands are dropping and we're losing 50 pounds per acre per day of CO2.
And it has impacts because as the island subside, the impact of sea
level rise and the likelihood of levee failure and the likelihood of
earthquake slumping levees increases with it. Next.

So, the USGS has been very instrumental in the program that I managed as
well as the Department of Water Resources we worked with the GS to do
this one. Actually understanding what causes subsidence. And then,
looking at these greenhouse gas emissions. Next. Now we understand it to
the point we actually know how to reverse it, we can do what nature did
over thousands of years since its last Ice Age. The land surface has
been rising up until man came in, started farming these lands and the
land surface will rise and keeping up with sea level rise. We've been
able to basically replicate and amplify what nature did over the last
7,000 years and capture carbon in the soil in accrete lines of
acceleration.

Now, and here just to give you an example of some of the USGS data that
has been collected. This is the kind of soil that's being accreeted,
2-1/2 over 2 inches per year of soil, we call that soil. We could
actually stand on it, its firm enough. When they core this stuff and
actually, when you core down into the peat soils, in these organic
highly peat soils they use cryogenic freeze. They freeze the soil and
flood out. We call those **peatsickles**.

And so looking at one of the big issues that we're dealing with of
course, global standpoint is how are we going to sequester carbon? In
the Delta, if we were to convert these farmlands back to wetlands, we
would be sequestering large amounts of carbon. We're currently losing a
lot of carbon as we show here as the U.S. data shows. We're losing these
50 pounds per acre per day. But if you compare other means for
sequestering carbon with actually with Delta wetlands and not growing
corn on some of these lands, you can see that in that net gain is fairly
significant. Next. And with that, I will open it up for questions and
I'll conclude my talk. Thank you."

(Applause)

**Bob Hirsch:** "Thank you Curt. And I want to thank the Interstate
Council on Water Policy, Peter Evans for sponsoring this event and
providing the refreshments. And thanks to all, everyone for coming. And
I want to mention that we're going to hold another briefing on, USGS
will be holding another briefing in July on the topic of The
Relationship Between Climate Change And Energy Resources. And I\'ll ask
our three speakers to come up front and they'll entertain questions. So
let's start seeing some answer. People who would like to pose questions
to one or all of our speakers. Yes, Perez."

**Perez**: "Yeah. Could you elaborate on the science behind salt
detecting salt water in the aquifers. How far along are we in terms of
determining whether that can happen, at what levels of sea rise would
that **occur**?"

"I can't give you much more detail."

**Bob Hirsch**: (Whispers) "You have to repeat the question."

"I'm sorry. The question was on this issue of sea level rise and threats
to water sources, what do we know a little more specifically, rather
than hand waving qualitative arguments like I was presenting. And I
cannot answer that myself very well. Bob may, actually say a little more
than I. The USGS has done a lot of work with salt water intrusion and I
think, I could just add some of these forcing functions on top of
existing ah, scientific analyses."

**Bob Hirsch:** "The measurement of salt water intrusion is not
particularly difficult if you have a long term observation well with the
sensor and its **presensing** specific conductance which is a simple
surrogate for salinity. So technically, it's not a terribly difficult
job. There's a lot of spatial variations so that measuring at any one
point doesn't necessarily tell the whole story.

The USGS actually has for many years done a lot of work on salt water
intrusion mostly because of the drivers of that salt water intrusion are
the use of water by municipalities in particular, coastal areas,
anywhere along the east coast, anywhere along the west coast. These
happen in major centers where there is heavy pumping on the aquifer. The
rise of sea level is simply one additional factor, an additional
stressor to particularly the pumping stressors or the direct local
climate effects. But the modeling in fact, the USGS has produced a
number of really outstanding...they're called multiple density models
because the trick in this kind of modeling is that, most ground water
modeling assumes a simple density of water which is fresh water. In the
case of salt water intrusion, it's multiple densities and how do these
two liquids, the saltier water and the fresher water behave? And we've
done a lot with that. And for example in South Florida would be one
prime example. More hands. Back here."

"This question is for \_\_\_. Do the modeling \_\_\_\_ what happen to
the levee? Did the modeling wave show you what happen when levees were
breached and salt water are intruded. How much will likely that this
would happen with rise in sea levels, is that possible now. Isn't it
possible now? Yeah, it sort of \_\_\_\_\_. Yeah there was a scenario
throughout \_\_\_\_\_\_ and what are the probabilities of that happening
and as the sea level arises, how does that risk go up?"

"There is an existing risk today. That risk, associated with the
scenario we paint, model here was about 2% in the next 50 years. If you
add sea level rise onto that, you're looking at a number of different
things that could happen. If you have this tidal amplification, you have
an increase in salinity intrusion and that salinity intrusion actually
almost doubles when it start flooding islands, critical islands in the
western Delta. So, um, because the islands act as a bix mixing machine,
blender, it actually could draw additional water into the Delta. So, the
added water needed to maintain what we call \_\_\_\_\_ which is a two
part per thousand salinity level. There is a significant increase, about
20% to 30% increase for a 3-foot sea level rise in the additional water,
you would need maintain that \_\_\_\_\_ otherwise you're going to let
salt come further into the Delta and obviously then you would
contaminate water supplies doing that. Does that answer your question?
So if, if we have a risk and that risk is magnified with the sea level
rise."

**Bob Hirsch**: "And, I would actually like to add another question to
that looking at the some of what Chris was talking about at the
hydrology or what's happening in the Sierra Nevadas is the potential and
I don't think we have any proof for this at this time. But the potential
for some of the massive winter storms that California is known for which
historically have put a lot of snow in the Sierras could, in the future
be more rain event, more so a rain event resulting in large scale
flooding which could be another causative factor in terms of these kind
of levee failures."

"Right, climate changes which like, Bob says brings on additional higher
run offs, you magnify that with a higher sea, then you create what's it
called the bigger backwater effect. And you'll see it's going to cause
more flooding in the levees. The other thing that's important to know
here is that because California operates its reservoirs in the winter
time, there's a certain amount of storage maintained in the reservoirs
for flood. If the floods are getting bigger, then you have to maintain
more flood storage which reduces the what we call conservation storage.
This storage that we carry over during summer months and we then use to
fill up with snow melt. If we have less snow melt and we have to have
the bigger floods and we're going to have less water in the reservoirs
and that less water in the reservoirs at the same time we're going to
have higher salinity intrusion in the Delta and we're kind of getting it
from all sides."

**Bob Hirsch:** "Did you want to add anything?"

"No that's basically it.'

**Bob Hirsch:** "Gene?"

**Gene**: "Ah, two questions for Kathy. Ah, when you say increase in
rain and an increase in ability to forecast drought, ah, I wonder what
you think water managers should do when a drought is forecast that's the
scenario. And the second question is have we established agricultural
areas using engineering structures that may have to be abandoned in the
future?"

**Kathy Jacobs**: "Okay, ah, starting first with how to prepare for
drought there is definitely a time scale issue here. I mean knowing 2
weeks before a drought is quite different from 2 years before drought
and knowing that it's going to be a 10-year drought as opposed to
2-month drought, I mean, you know, those are all entirely different
alternatives.

And part of what you would do in advance is something you can actually
sort of trigger immediately such as a drought strategy for reducing
water demand at a particular time. But if you have more advanced notice,
you can do things such as triggering a dryer option agreement with a
farmer who has agreed to give you their water supply in exchange for
money in advance, um, so that in the future, if you know you're heading
into a drought season, you can actually ask the farmer not to farm and
move that water into the municipal water supply arena.

Another way, they can respond is the way they operate dams, reservoirs,
and diversion structures. Those are all operations decisions that
depending on what time scale the information is on, you might behave
very differently. But when you're looking out into the extremely long
term as we are with climate change, what we're really talking about is
long term adaptation, such as in Arizona, storing as much water
underground as possible, not knowing what year it's going to be used.
But at some point in the future, you know the Colorado River supplies
are going to be cut off and so you really need to start storing water
during surplus periods if there are any. That's of course the trick.

As far as do we need to rearrange the way we do deliveries to
agriculture as part of a drought strategy, we already are. I mean,
that's a part of what's going on in southern California lining ditches
and there are in fact already some water transfers going on, both short
term and long term between agricultural entities and municipal entities.
That's with the main movement is at the moment. Thanks."

**Audience Question**: "Ah, a question for the first speaker. Ah, some
\_\_\_\_such as what are the predictions that we often hear for
\_\_\_\_\_ changes and increase in intensity \_\_\_\_\_\_\_\_. You know
the maps that show that coastline ah, across the U.S. \_\_\_\_\_\_\_
more intense and stronger?"

**Chris Milly**: "Right. So the question is saying I've talked about the
means, what about the hypothesized increases in variability on top of
that. I do not have such maps. Our group has not done that analysis.
We're doing that sort of an analysis right now. Some people have put
forth some data that they say supports that hypothesis. That's about all
I would say about that right now. Thank you."

**Bob Hirsch**: "Ah, let me take my chairs prerogative and also comment.
Extreme storm events, be they thunderstorms or hurricanes or, or
anything in between are really very difficult matter for the present
generation climate models to really describe and predict those kinds of
behaviors because much of those behaviors really are of finer spatial
scale,

than the models can handle. And I think in the future, we'll see that.
The empirical analyses of historical data, particularly on floods, I
would say is very, very equivocal at the present time. As to whether
we're seeing any kind of a real change in the natural magnitude of
flooding, we have huge increases in flood damages in the United States.
But that's due to the human phenomena the way that people occupy the
flood plane. But as to the phenomena of flooding and whether it's
changed, it's statistically a very difficult thing to determine and I
think they are really a real mix of results at the present time. Peter."

**Peter**: "I heard Dr. Jacobs talk about storing water potentially
groundwater, groundwater water banking in the future. Is that going to
become kind of modus operandi for the west and some part to deal with
these droughts? What do you think is the role of the Federal Government,
USGS, how they get to help you figure out what kind of storage capacity
you have and those kind of questions? Or what is, is there a role?

**Kathy Jacobs**: "The question is how the federal government can help
in trying to figure out where we can store water in the future and
aquifers and actually the United States Geological Survey already does a
lot of that kind of work. They do a lot of ground water modeling. They
actually characterize aquifers so that, that makes it possible to know
where you can store water and how quickly water moves in what kind of
substrate. So at least in Arizona they've already played a really
significant role. The state of course also plays a role in terms of
regulating these facilities and permitting and permitting both the
storage and the recovery in looking at the water quality implications
for the aquifer but there is no doubt that the Federal Government
probably needs to do it for its purposes in addition to supporting it
through science. In other words there are federal facilities and
resources that need to be protected to ensure that water supplies are
adequate for federal reasons and so there may be, you know, extension of
that kind of activity. But historically, there has been a support role
and I anticipate it will only increase."

**Bob Hirsch:** "And again, let me just add a little comment. We are, in
the USGS is very engaged really throughout the United States on studies
of aquifers storage and recovery and the science to underpin that
engineering. And if I can make an analogy, if you look at the 20^th^
century up through the 1970s or so where the primary technology for
storing water for water supply the surface water reservoirs, the Federal
engineering agencies, Bureau Of Reclamation and Army Corpse of Engineers
and the USGS contributed large amounts of basic science and engineering
techniques, etc. that would underpin people making those design and
management decisions. I think that the storage technology of the future
is going to be more and more groundwater as the way that that water is
stored and there are similarly important engineering and science
questions. How do you get that water in the ground? How sustainable is
your ability to get it into the ground? What are the geochemical changes
that occur that can underpin that and I think basic research again by
the engineering agencies and by the USGS I think is crucial."

"I think part of that question is also how do you know how much storage
you're going to need given the changes that are forthcoming and you
know, water managers have methods for looking at it statistically at the
history and assessing risk of not meeting water supply. What they really
need to do? The simplest approach is sort of putting overlaying these
trends on top and so we can begin by saying these are our best guesses
of those trends. They can say how much they believe that overlay that
into their own analyses and over time, I think those projections will
get tighter and tighter."

**Bob Hirsch:** "Over here."

**Audience Question:** "What if there's any use of the USDA resources,
one of the farmers \_**1:02:53**\_\_\_ conservation \_\_\_\_\_.?"

**Kathy Jacobs:** "The question is whether the USDA is engaged in this?
Absolutely. There is a very large investment in conservation activities
through the equipped program and several other programs that the USDA
pursues and in fact, USDA is a partner in many climate science
applications. They are actually are involved in creating some of the
river flows in the west. So they are partners with multiple other
organizations that form essentially a network of observations, as well
as in implementing conservation practices."

**Bob Hirsch:** "And I'd just like to support that. We've talked a bit
about the importance of our streamgages and I would really strongly
emphasize the importance of the department. NRCS snow surveys because as
Chris described, one of the most critical near term climate questions is
what kind of effect are occurring on snow pack in the NRCS snow surveys
are absolutely crucial to that."

**Audience Question:** "Bob you mentioned that historically, ah, USGS,
engineering agencies **\_\_\_\_** from the forest are gone. \_\_\_\_\_
in where, where reservoirs should reside and things like that. What's
currently being done through request \_\_\_\_\_ others and helping the
other forests \_\_\_\_\_ federal reservoirs. There's a lot of talk about
expansion of federal reservoirs in southern California. The governors
then, um, proposed a new dam in the state of California. Some of those
sites where first identified in the early 1900s of where some of those
dams are going to be located. What's the give and take between the
agencies ah, to make sure that climate change or these trends that
you're seeing is incorporate and the new reservoir site locations?

**Bob Hirsch:** "I'm not familiar with us being directly engaged in the
studies of some potential new surface water reservoir sites. We are much
more engaged in really looking at ground water, typically with
municipalities through our cooperative water program and we're there
looking at some of the potential ground water storage sites. Now, our
hydrologic data are crucial to those. The models like Chris talked about
are crucial to, back to the surface water. Our stream flow data, the
kind of models that Chris described, and USGS seismic data which
particularly in California is always a really critical factor in the
reservoir sighting and design questions as what's the seismic risk that
has to be designed for. But I'm not, nothing come into my mind
immediately of a direct current involvement in looking at reservoir
sighting other than those general kinds of things that we do."

**Audience Question:** "I, I've a couple of questions about the
expansion for Chris Milly. I'm just interested in ah, when you have get
started, things like these, \_\_\_\_\_ model type, there seem to be a
big problem going on in my \_\_\_\_\_, is the water \_\_\_\_\_.
Historically, I'm just curious if you knew what was going on there?"

**Chris Milly**: "Right. And I don't if I would focus on the discrepancy
so much as acknowledge that throughout that map, there were things that
may be didn't catch your eye. There's a few, sort of isolated circles
that do catch you eye. There are regional ah, weaknesses in the models.
It's not sort of a homogeneous error. They are centered in some areas
and in fact, you can look at the control simulations. The basic present
day simulations and see certain reasons where the models tend to do less
well than they do in other regions and those tend to be the regions
where they tend to get the trends wrong also. So, no simple answer but
it's just, you're just underlining the point that yes, we have ways to
go. But also there is natural variability and even a perfect model and
we'd shown this. Even with the perfect model, there would not have been
perfect agreement there because of natural variability in the historical
record. It's only one realization of a random process."

"And now, okay. I suppose \_\_\_\_\_. You told \_\_\_\_ ensuring the
supply, what was the other side of that is the demand, when \_\_\_\_ key
strategies if they're changing demands as like in changing agriculture,
um, different propriety \_\_\_\_\_ um, regulation of course would be...

**Kathy Jacobs:** "The question is how do we deal with the demand side
of the equation. And there is in fact increasing interest in that side.
And there are parts of the west where already very dramatic conservation
programs are in place. But a lot of it has to do with incentives and
trying to convince the public and those who are making decisions about
using water, ah, that it's worth their while to conserve it. And one of
the issues we're actually facing in Arizona is the perception that if
they conserve water, more people are simply going to move there and
drink.

And so, we need to be very clear about why we're conserving water and,
that is actually a significant political consideration. There are also
all kinds of economic ways that we can provide more incentives for
people to conserve water. At this point, there are almost no economic
incentives for many in agriculture to conserve water because their water
is so inexpensive, while others may be paying \$500 or \$600 an
acre/foot. I mean, there's a dramatic disparity in cost. We aren't
really able to control the cost of water in most circumstances so it's a
combination of economic incentives and sort of political messaging and
technological advances. There's no real easy answer here."

**Bob Hirsch**: "David."

**David**: "Bob, um, to all of the speakers. This issue of ground water
and the importance of ground water, I think I'm hearing a lot of things
that cause me to bring to question about this. Ground water particularly
in the drought problem area like, we're going to see more of this in the
southwest and California has been, it seems to me a very important
factor in the last 20 years, for most municipalities in the region in
terms of managing water supplies. More attention, I think over the last
50 years seems to have gone at the federal level toward surface water
development. But a lot of the local governments and water agencies have
also focused a lot of quiet intentions to ground water. What are the
potential? And with global warming, every time you build a surface water
facility, you have a lot of evaporation and global warming seems to me
to suggest that that evaporating is significant and might be worth
focusing on. And then, I guess the last part of this question, because
that is a question (laughter) is ah, what is the potential for ground
water management? I mean have we scratched to the surface or is there a
lot more potential there than we realize? And what are water managers
doing about that?"

"Let me start with some of the physical answers and then move to the
management answers. The, what I call the run off of water availability
would apply also to ground water recharge, number 1. So those arid
regions are projected to be receiving less ground water recharge. Number
2, surface water, yes you're absolutely right, we expect that water
demands for agriculture as water demands from free water surfaces of
surface water reservoirs are going to consume more water. Number 3,
ground water, there's some question whether recharge even for a given
amount of precipitation could be reduced due to storminess of
precipitation versus the gradual snow melt and also due just to the
increased intensity of precipitation that has been put forth by some. So
I'll just stop there and turn it over."

**Kathy Jacobs:** "Ah, well the good news about dewatering aquifers is
that it means that there is space to store water so, there actually is a
semi-silver lining. Arizona has more than 7-day recharge facilities
right now. Some of them are direct recharge facilities and others are
essentially exchanges with farmers where we're saving their ground water
and giving them surface water on a temporary basis in exchange. There is
no doubt that we have far more potential to use aquifers as storage
mechanisms. And actually I don't think there's any argument that
Arizona\'s led the way in terms of the institutional arrangements that
are required for storing water and protecting once it's stored and
protecting the ability to recover it.

But to the extent that we are starting to use these aquifers as storage
mechanisms, there are all kinds of other implications including water
quality implications that need to be paid attention to. There is no
doubt there is substantially more potential to that all over the
country. It is expensive. It does require a lot of science and people
don't understand how water behaves underground. So there's a risk there.
It's not as palpable as actually seeing whether or not your bathtub is
full. You can't necessary tell where it's going. But Arizona is
committed to it, California has been doing it for decades. It's very
popular in many parts of the country. Different techniques are used in
different kinds of aquifers, but there's a lot of potential."

**Audience Question**: "\_ \_\_\_ answer ah, my question which is what
would data and models say about changes \_\_\_\_\_ the global warming to
areas such as Hudson River, where \_\_\_\_\_ constituents reside. I'm
sure there'll be questions about whether ah, global warming is causing
all these flood and what does that mean \_\_\_\_\_?"

**Bob Hirsch:** "Want to try?"

The Hudson River Valley, so what?"

"Hudson River Valley, yeah."

"Hudson, New York, right? Yeah, but what specifically can we project for
the region of the Hudson River Valley, of course, we're always hesitant
to get more specific and more localized of the space, but some general
things that can be taken away from this are number one, salinity is
likely to intrude more frequently farther up the Hudson River, for the
given distance of intrusion is more likely to occur of course. Secondly,
New York state receives a lot of its precipitation as snow fall and so
it is vulnerable to this shift in the seasonal distribution of the run
off and that may or may not an issue and it may in particular be an
issue for flood risk especially if there is a little bit of an increase
of precipitation on top of that. Let me step back and think about
anything else that, Bob?"

"I got specific\_\_\_\_\_\_\_ asked questioning, but ....

**Bob Hirsch:** "Right. I think it goes back to one the comments I made
about flood potential. And I've certainly just in the last few years,
the data are suggestive both on the Delaware base and the Hudson base
and in various places in New England suggestive of an increasing flood
risk including the nor-easter just two weeks ago. But I think we all
have to be very cautious. It's always like, you know, you go out on, in
January everybody was talking about, this is obviously global warming
where it's 74 degrees in Central Park. And then 2 weeks ago, we were all
freezing in this part of the country and rapidly jumping to conclusions
about one or a few extreme events, we need to be extremely cautious
about it. And I think that this whole issue of looking at the extremes
and looking at what the data tell us is something that's clearly, I
think on our horizon, on our research agenda. I don't think either from
the climatics modeling side or the hydrologic side that we have any
particular insight yet on changing risks of flood or drought other than
these broad patterns of changes in overall water supply."

"I'm going to followup. I, I preclude that the idea of increased risk of
flood is a bit early. I distanced myself a bit, but I don't and I agree
with Bob that the evidence is equivocal. On the other hand, I suppose I
should've mentioned since we did research on in ourselves that when we
look from a global perspective at the number of events, very extreme
100-year floods on very, very large river basins. At points we can start
to resolve those scales with a climate model. We found that the models
are suggestive of increasing frequencies 20^th^ century. And we also
looked at the data and saw that the data were moving in the same
direction, more or less consistently with the model. Both the model and
the data said, well at this point in time, you should expect things to
be sort of equivocal when you look at the data. So we couldn't narrow it
down to the Hudson River basin, but we could say from a global
perspective there does appear to be some evidence of that."

**Audience Question**: "This is a good question. Of course you invest
your reluctance about getting more specific, but perhaps, I mean, if you
could say a little bit more about those shifts you described from snow
fall to rain fall. Is it, is it, um, as much a shift in time is it or
getting the precipitation later in the year or is it coming earlier or
early as if you would, but it's raining instead of snowing?"

**Chris**:

"Of course, both of those are true, I mean there are shifts in the
distribution of total precipitation. Conceptually in my head I was
talking simply about the same time distribution of precipitation but the
form of the precipitation changing from snow to liquid. And I tend to
decouple that in my head from an additional issue on top of that of
changes in total amount but also seasonality. To first order
seasonality, we're not going to see great shifts in total precipitation
distribution through the year. Places where the summer are maximum will
tend to continue to be places of summer maximum and so forth."

**Bob Hirsch**: "Let me add a couple other thoughts to that recent paper
published by Dr. Noah Knowles of the USGS on others looking at many,
many climate records from here throughout the Sierra Nevada and other
parts of the western United States. A very clear pattern of the ratio of
rain to snow during the colder months of the year, that ratio of rain to
snow at a given station has significantly increased. Not that the amount
of precipitation has changed particularly but that that ratio has
changed.

And switching to the eastern United States, looking in New England,
places like the state of Maine particularly some of the coldest areas
when you look at, again see that change in the form of precipitation and
you can look that the run off that occurs, the stream flow that occurs
and in fact you can find very, very large increases in run off say in
the month of February because of rain events and melt events that never
used to occur and very substantial decreases in run off in the month of
May because the snow pack has already left where as in the past it
hadn't. And yet interestingly, at those very same sites with strong
trends in those particular times of the year, no trend were essentially
in the total amount of run off occurring in the system. So, it's not
just about, is it generally getting wetter or getting dryer, but some
these seasonal distributions of the type of precipitation and the timing
of melt. Over here."

**Audience Question:** {question not clear}

Bob Hirsch: "Do you want to say anything about remote sensing and
thermal imaging?\"

**Kathy Jacobs**: "I can't speak for um, the issue of whether or not the
USGS got plans to deal with (cough) excuse me. But I will say that
Arizona has in fact been using these images not specifically to evaluate
whether more water is being applied to a particular that it is supposed
to be, but certainly in the context of monitoring for illegal irrigation
because we actually have restricted which lands can be irrigated and so,
using satellite imagery, you can tell whether or not land is being
irrigated that wasn't supposed to be. There's many there's many
satellite based opportunities to measure even the water in aquifers, to
the grace program that uses gravity to figure out how much water, with
the changing storages and underground aquifers that's another useful
way. We use satellite imagery for actually measuring subsidence and land
surface. The variety of different opportunities to use those
technologies and in studying the whole water cycle and **\_\_\_\_**
transpiration and the connections between ocean and atmosphere, that's
our part of what builds these global climate models."

**Bob Hirsch**: "Let me address your question about the USGS and the
budgets, etc. We're very well aware of this issue and the importance of
a thermal band and LANDSAT and very continuity of LANDSAT. This is a
very important program to the USGS. On the thermal band issue,
interestingly next week, I'm going to be attending a meeting at the
Western States Water Council at EROS Data Center, at Sioux Falls, South
Dakota and we'll be talking with USGS scientists there who are experts
on that. It's been a big issue among water managers. We are concerned
about that budgetary issues as we're concerned with a lot of tough
budget issues, whether they be streamgages, ground water monitoring
sites or thermal bands or simply very tough priority decisions that have
to be made. That thermal band decision is one of those tough decisions,
but we are fully cognizant of the great value of that program. Let me
take one final question and then we'll close, if there are. I thought I
saw some more hands. John."

**Bob Hirsch:** "Okay. Over here."

**Audience Question**: "Ah, I found the presentations very interesting.
What's the likelihood that the presentations will be up on the USGS
website?"

"100%."

**Bob Hirsch**: "100% probability that it will be up on, how do we
direct people to..?

"Um, we can give you that website on your way out, okay?"

**Bob Hirsch**: "Okay?"

"usgs.gov/solutions" (laughter)

**Bob Hirsch**: "Um, okay. We'll call it officially closed. The speakers
and I will stay here for a few more minutes to, if you want to engage us
in conversation. Thank you for your great interest. And let's thank the
speakers for outstanding presentation. Thank you all for coming."

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