2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Water Cycle Dynamics in a Changing EnvironmentAdvancing Hydrologic Science through Synthesis

to organize and employ synthesis activities to produce transformational outcomes that will be utilized to improve the predictability of water cycle dynamics in a changing Earth environment.

Objective

Hydromorphology: Human-Nature Interactions #1. Interactions between hydrosphere and biosphere processes #2. Interactions of landscape processes within intensively managed watersheds Evolution, structure and function of hydrologic subsystems in hillslopes Stochastic transport in heterogeneous media

Research Themes

Principal Investigators: Murugesu Sivapalan, Praveen Kumar, Bruce Rhoads, Don Wuebbles

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Unprecedented Types, Rates, Scales, and Magnitudes of Change

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Limits to predictabilityPrediction means making probabilistic statements about future system states given the current and past observed states and our understanding of how nature works. The four classical limits to predictability are (NRC WSTB, 2002):• Type I – uncertainty in the characterization

of initial states• Type II – uncertainty in the characterization

of the dynamics at the interfaces• Type III – uncertainty in the

characterization of model parameters• Type IV – uncertainty or inadequacy of

characterization of critical processes, process interactions and feedbacks

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Working Hypotheses: Patterns

• Patterns help us to reduce the complexity through reduced dimensionality, and thus help to improve predictions

• Patterns (both observed and so far unobserved) are emergent properties arising out of complex interactions and feedbacks between a multitude of processes.

• Study of patterns (how to describe them, why they emerge, their impact on the overall response) yields new insights and lead to increased understanding.

• Study of observed patterns (why they emerge) may give insights into unobservable or as yet unobserved patterns, and help to make improved predictions

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Theme #1: Interactions between hydrosphere and biosphere processes

Water balance partitioning at the catchment scalePeter Troch, Ciaran Harman and Sally Thompson

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

The Horton Index

Precip

“Fast” runoff

“Slow” runoff

ET

Wetting

Annual Evapotranspiration

Annual WettingHI =

Proportion of available water that is vaporized

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Horton Index vs. Humidity IndexBetween catchments

Troch et al., 2009 (HP)

Between yearsPattern that intrigues…..

Humidity Index =Annual Precipitation

Annual Potential Evaporation

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Horton, 1933 (AGU)

H constantVW

V : Growing-season vaporization (E+T)W : Growing-season wetting (P-S)

“The natural vegetation of a region tends to develop to such an extent that it can utilize the largest possible proportion of the available soil moisture supplied by infiltration” (Horton, 1933, p.455)

Pattern that intrigues…..

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

MOPEX catchments

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Models of landscapes as nonlinear filters Penman Monteith

Model

Rn VPD LAI U P T

Emax

E

T

Interception Model

PPT

Runoff

Drainage

Infiltration

Multiple Wetting Front Model Root Water Uptake Model

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

FLUXNET sites

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Hypothesis

?

?

?

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Theme #2: Interactions of landscape processes

within intensively managed watersheds

Sediment and Contaminant Dynamics Across Scales Nandita Basu, Ciaran Harman, Sally Thompson

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Patterns that intrigue…..

Nitrate load-discharge relationships across Mississippi

Sediment load-discharge relationships

Why are they linear?Or,

Why are watersheds chemostatic?At what scale are they chemostatic?

And why?

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Filtering of solute variability across scales: Study sites

Mississippi Basin

Little Vermilion

Single Tile Drain

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Landscape and Network Filtering of Sediment Transport: Study Sites

Goodwin Creek, Mississippi Rio Isabena, Spain

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Hypothesis: Landscapes act as cascading,coupled filters

Observed “patterns” are windows into this filtering

2009 Hydrologic Synthesis Reverse Site Visit – Arlington VA

Summary• Summer institute: grassroots type organization – team based,

egalitarian, targeted and yet free to explore alternative ideas or approaches, trail blazing

• Data based: recognize/extract patterns from data• Patterns needing a multitude of perspectives from different disciplines

to explain or interpret• Interpretation of patterns using parsimonious models: a top-down

approach• What are the minimum processes needed to describe strong physical, chemical

and biological coupling over a wide range of spatial and temporal scales?• How do complex highly heterogeneous physical, chemical and biological systems

respond to changes in forcing behavior and system structure?• Comparative hydrology: develop generalizable insights through

comparisons and classification• Modeling of landscapes as nonlinear hierarchical filters –

potentially transformative approach