Observations and Thoughts on Water Resources Research

Ximing CaiVen Te Chow Hydrosystems Laboratory

Department of Civil and Environmental EngineeringUniversity of Illinois at Urbana-Champaign

xmcai@illinois.edu

Outline

• Pressing challenges in hydrology

• Stronger scientific support needed for water

resources management

• Recent shifts in hydrologic studies

• Outlook to future research

2

Chronology of Water Governance Concerns

in the US

• Navigation 1787-1830s

• Land development

(Swamplands) 1850-1900

• Irrigation 1902-1940

• Drinking water 1912-1960

• Power generation 1920-1960

• Flood control 1930-1965

• Recreation 1945-1960

• Water pollution 1948-1980

• Ecosystem restoration 1980-1990

• Sustainability 1990-2000s

3(Courtesy to Prof. Peter Roger, Harvard Univ.)

Trajectory of Hydrologic Studies

• Geographical hydrology

A branch of earth science on water cycle & water balance

• Engineering Hydrology

Also called water resources engineering, a civil

engineering specialty concerned with the flow and storage

of water

• Environmental Hydrology

A unified approach to the role of hydrology in

environmental planning and management

• Eco-hydrology

An interdisciplinary field studying the interactions between

water and ecosystems

• The next is to support sustainable water

resources management !? 4

Trajectory of Hydrologic Studies

What is next? • Socio-hydrology? A science for water and

people!? (Sivapalan et al., Hydrol. Process. 2011)

Humans have changed the way the world works. Now they have to

change the way they think about it, too. The Economist, May 26,

2011

• Hydromorphology ? Identifying human footprint

in hydrologic processes (Vogel, J. of Wat. Resour.

Plan. and Mgmt, 2012)

5

Hydrology: The Interdisciplinary Science

of Water

• Adequate understanding of hydrologic systems

for water resources management requires

consideration of the coupled human/

hydrologic system

• Human and physical processes will be joint

predictor of hydrologic response

(Vogel, Lall, Cai, et al. 2015, WRR)

Pressing Challenges

7

• Weak representation of the human dimension

in hydrologic systems

• Disciplined studies on the human dimension

and the nature dimension without a

systematic handling of the interaction and

feedback between the two

From the STANFORD MODEL TO BASINS:

Distributed watershed hydrologic modeling

• HSPF Release 5.0 (1980),

12.0 (2001) …

• The Hydrologic Modeling

System (HEC-HMS)

• Soil and water Assessment

Tool (SWAT, 2003-2012)

• Storm Water Management

Model (SWMM, starting

form 1971) for Urban

Watershed Management

• MIKE-SHE

• More …

8

• Human input data errors are usually biased,

unknown or not fully known, which can be

converted into model parametrization and

prediction (Hejazi, et al., 2008, J. Hydroinformatics;

Wang and Cai, 2009, AWR)

• Nonlinear responses to human inputs (Thomas et

al. 2013, WRR; Wang and Cai, 2009, WRR)

• Empirical hydrologic relations are violated by

human interferences (Wang and Cai, 2009, AWR)

Why do we need to care about human

interferences in hydrologic modeling

9

Nonlinear responses to human inputs

10

Republican River Basin (RRB), Midwest, US

11

In the RRB, long term average P≠Q+ET

In dry years, ET >P; in wet years, ET<P but Q remains low

Frenchman, Republican River Basin

0

200

400

600

800

1000

1200

1400

1983 1987 1991 1995 1999 2003 Year

PET

/P

/ET

/P

um

pin

g/R

un

off

(m

m)

PET Precip UM_ET Pumping Runoff 12

Aquifer storage change in the RRB: storage depletion

over years

P=Q+ET + S multiple year average S ≠ 0

13

Aquifer storage change in the RRB: Altered

seasonal patterns

Pre-development: Summer recharge and winter discharge After-development: Almost opposite direction and the recharge-discharge balance does not maintain

(Zeng and Cai, 2013, HESS)

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

Jan Mar May Jul Sep Nov

Wat

er

De

pth

[m

m]

Pre1950s(RRCA)

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

Jan Mar May Jul Sep Nov

Wat

er

De

pth

[m

m]

Pre1950s(RRCA)

1951-1960

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

Jan Mar May Jul Sep Nov

Wat

er

De

pth

[m

m]

Pre1950s(RRCA)

1951-1960

1961-1970

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

Jan Mar May Jul Sep Nov

Wat

er

De

pth

[m

m]

Pre1950s(RRCA)

1951-1960

1961-1970

1971-1980

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

Jan Mar May Jul Sep Nov

Wat

er

De

pth

[m

m]

Pre1950s(RRCA)

1951-1960

1961-1970

1971-1980

1981-1994

14

–dQ/dt ~ Q and the recession slope curve for Salt Creek during

the summer of four time periods

10-1

100

10-3

10-2

10-1

100

Q [mm/d]

-dQ

/dt

[mm

/d2]

Summer, 1946-1953, Salt Creek

10-1

100

10-3

10-2

10-1

100

Q [mm/d]

-dQ

/dt

[mm

/d2]

Summer, 1954-1965, Salt Creek

10-1

100

10-3

10-2

10-1

100

Q [mm/d]

-dQ

/dt

[mm

/d2]

Summer, 1966-1985, Salt Creek

10-1

100

10-3

10-2

10-1

100

Q [mm/d]

-dQ

/dt

[mm

/d2]

Summer, 1986-2005, Salt Creek

1946-1953 1954-1965

1966-1985 1986-2005

(Wang and Cai, 2009, AWR)

15

Inter-year variability of ET depends on land uses

y = 0.2931x + 0.2411

R2 = 0.9444 y = 0.2326x + 0.2762

R2 = 0.9054

y = 0.1495x + 0.193

R2 = 0.8186

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

PET/P

ET

/P

22.5% Frenchman, RRB10.4% Upper RRB 1.7% Upper PecosWater-energy limit22.5% Frenchman, RRB10.4% Upper RRB 1.7% Upper Pecos

(Chen et al., 2011, 2012, WRR)

The percentage represents the fraction of irrigation land coverage

16

Outline

• Pressing challenges in hydrology

• Stronger scientific support needed for water

resources management

• Recent shifts in hydrologic studies

• Outlook to future research

17

Achievements of the Harvard Water Program

The Harvard Water Program (initialized in late 1950s)

• Interdisciplinary studies: especially hydrology and

economics

• Computer simulations, synthetic hydrology, streamflow

synthesis and system operation

• Systems analysis and operations research: multi-

objective optimization

• Wide applications to water resources system design

The landmark text by Maass et al. (1962):

Maass, Arthur, Maynard M. Hufschmidt, Robert Dorfman, Harold A. Thomas, Jr., Stephen A.

Marglin, and Gordon Maskew Fair. Design of Water-Resource Systems. Cambridge: Harvard

University Press, 1962.18

Criticisms on the Harvard Water Program

‘‘The question is whether one would rather be right or be

President. As a scientist, I would rather be right; but as an

engineer concerned with water-resource planning, I would

rather be President’’ Fiering (1997)

“…Harvard colleagues spent less time looking for the

exact ‘‘right model’’ and more time trying to provide

reasonable answers to both political and economic

questions” (Reuss, 2003)

It is the time to resurrect the Harvard Water

Program with a larger focus on science (Reuss, 2003)19

Gaps in knowledge & scientific research needs

• The long term socioeconomic effects of water investments

and policy choices

• The behavioral economics and political science of how water

is actually allocated in practice

• Prediction and valuation of ecological responses to alternative

water use, flow and investment regimes

• •Feedback effects of water use on local hydrology and

hydrometeorology

• Simulating/predicting observed water system operations

• • Predicting the evolution of water demand

The Future of Water Resources Systems Analysis: Toward a scientific framework for sustainable water

management, Brown C., J. Lund, X. Cai, P. Reed, E. Zagona, A. Ostfeld, J. Hall, G. Characklis, Wi. Yu, L.

Brekke, WRR.

A stronger scientific approach is needed:

• Evidence of the scientific validities of the models used

• Scientific explanation of the status of water resources

systems, and

• The basis for predicting the effects of future

exogenous factors and policy choices

What is needed to be “right”

Outline

• Pressing challenges

• Better scientific support needed for water

resources management

• Recent shifts in hydrologic studies

• Outlook to future research

22

The focus of hydrologic studies is shifting

• from local to global spatial scales

• from short to longer time scales

• from single hydrologic processes to an integrated analysis of the water cycle with increasing interdisciplinary connections

• from the focus on physical systems to coupled nature-human systems

(Montanari et al., Legacy and Perspectives for the Science of Hydrology, WRR, 2015)

Frequent used words in WRR papers

(Rajaram et al., A Reflection on the First 50 Years of Water Resources Research, WRR 2015)25

CategoriesNo. of Papers

The legacy of hydrological

sciences 8Water

processes interpretation and modeling 23

Water Resources, society and

Water Threats 22

Papers accepted for WRR 50th Anniversary Special Issue

26

Outline

• Pressing challenges

• Better scientific support requirement from

water resources management

• Recent shifts in hydrologic studies

• Outlook to future research

27

Use-inspired science

Use-inspired science (Stokes, 1997):

o addressing urgent sustainability problems

by integrating existing scientific theories

& methods (e.g., integrated assessment,

DOE)

o creating new knowledge and

understanding of emergent system

dynamics (complex systems)

28

The growth of coupled human-nature system (CHNS) and the co-evolution of the two systems

(Source: Loucks and Van Beek, 2005)

29

• Inflows = Outflowsbut some inflows and outflows are affected by human activities

• Energy balanceConsiderable energy is imposed to the system by humans

• System dynamics: driving forces of energy and water flow marginal value of water?

Developing Principles for CHNSConnectedness between hydrologic and social systems are required for

understanding the interactions, feedbacks and the system dynamics

• System equilibrium: co-evolutionof coupled social and bio-physical changes driven by mutual causal interactions and feedbacks

30

Ecologists measure the resilience of the system as the amount

of disturbance required to push the system from one basin of

attraction to another (bottom diagram)

Resilience of a CNHS

(After Liu et al. (2007), Ambio.)

Water quality

31

Research issues under changing conditions

• Natural vs. human needs

• Simple vs. complex systems, e.g. food, energy and water

nexus (FEW, system of systems)

• Local vs. basin: spatial variability of impacts

• Temporal development of impacts: short vs. long term

(e.g., creeping environmental impacts)

• Stationary vs. non-stationary: Managing mean vs.

managing variability: Adaptive management, e.g.,

alternative wetness and dryness

• Water allocation vs. water reallocation

What is the role of hydrology?

Water reallocation shows great promise

as an adaptive water management tool

Water reallocation• is needed when the

existing allocation is physically infeasible

economically inefficient

socially unacceptable

• calls for integrated

supply & demand

management33

Initial stageDevelopment

stage

Depletion stage

Reallocation

Research opportunities for modeling CHNS

• Assessing water resources development and water use behavior and its

change due to environmental change

• Quantifying hydrologic response to human interferences especially the

nonlinearity of the response, crossing spatial scales and over time

periods

• Conducting experiments of integrated models with inference engines of

the co-evolution of H and N systems (e.g., coupling agent-based models

with environmental models; data-driven models)

• Establishing theoretical/empirical connectedness in the boundary of H

and N systems

• Addressing the interactions between natural uncertainty and bounded

rationality of human behaviors in risk-based decisions

• Supporting institutional reforms by scientific evidence & rationale

Big Data with sensors and other facilities, innovative observatory

programs, computing power, and cyber-infrastructure (e.g., global

data access) provide great opportunities34

Next generation of watershed models

Scientifically

sound

∩

Institutionally

realistic(Distributed

decision

modeling)

∩Computationally

tractable

(Distributed

hydrologic

modeling)

35

Tools that can be used to address sustainability

issues and explore scientific understanding

Thanks!

36