Sociohydrology: A new science of people and water


HYDROLOGICAL PROCESSES
Hydrol. Process. (2011)
Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/hyp.8426
Socio-hydrology: A new science of people and water
Murugesu Sivapalan,1,2*
Hubert H. G. Savenije3 and
Günter Blöschl4
1 Department of Civil and
Environmental Engineering,
Department of Geography, University
of Illinois at Urbana-Champaign,
Urbana, IL 61801, USA
2 Department of Civil and
Environmental Engineering, University
of Technology Sydney, Broadway, NSW
2007, Australia
3 Department of Water Management,
Faculty of Civil Engineering and
Geosciences, Delft University of
Technology, Delft, The Netherlands
4 Institute for Hydraulic and Water
Resources Engineering, Vienna
University of Technology, Vienna,
Austria

*Correspondence to:
Sivapalan, Murugesu, Geography and
Civil and Environmental Engineering,
University of Illinois at Urbana-Champaign
E-mail: sivapala@illinois.edu
Received 10 November 2011
Accepted 14 November 2011

Copyright © 2011 John Wiley & Sons, Ltd.
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
THE COUPLED HUMAN-WATER SYSTEM
Dateline November 2010, Murrumbidgee River Basin, Australia: Irrigators
are up in arms over proposed government plans to cut their water
allocations and return flows back to the basin’s rivers to support the
environment and restore lost biodiversity. The Australian of November 04,
2010 reported on the community backlash, including the resort to ‘book
burning’ to highlight their plight. Community backlash and ‘book burning’
notwithstanding, the reality is that this conflict had been brewing for
decades. Now, wind back the clock 100 years to the early 20th century. Up
until 1900, there were virtually no dams and almost no irrigation on the
Murrumbidgee. With demand for food for a growing population and the
possibility of generating agricultural exports, irrigated farming expanded
along the river corridor from 1920 onwards. By 1940, abstractions during
low flows had increased to 50% of the natural flow and by 1950 to almost
100% (Roderick, 2011). Over this period, the predominant direction of
farming development, construction of water ‘assets’ (e.g. dams and weirs) as
well as water extractions was upstream. However, things came to a head in
the 1980s, with increasing deterioration of river health and the recognition
that previous farming practices were no longer sustainable. Protection of the
environment was on the political agenda, along with a commitment not only
to return water to rivers to nurse them back to health, but also to help
agricultural industries to rise up to the challenge of a drier future. After
30years of seemingly ongoing crisis conditions, a protracted drought and a
looming federal election precipitated government action in early 2007. The
result was a concerted plan by government to buy back water rights of
willing farmers and build new assets aimed at increasing water use efficiency
and protecting the environment [Murray-Darling Basin Authority (MDBA),
2010]. For example, there has been an increasing trend for upstream rice
growers to sell back their annual allocations, and for downstream
horticulturalists to purchase fresh allocations during low allocation seasons.
This meant that, from 2000 onwards, water abstractions as well as water
assets that had been migrating upstream in the early 20th century are now
beginning to move back downstream (Figure 1). Whereas the sole customer
for 100 years was irrigated farming, now there is a new ‘customer in town’,
called the ‘environment’. More and more, much of the business of water
management in the basin, including the building of new assets, is aimed at
satisfying the environment, a phenomenon that wouldn’t have been foreseen
in the heady days of irrigation development and dam building. No wonder
the irrigators are up in arms.
If the competition between irrigation and the riparian environment

continues in this way in the Murrumbidgee over the next decades, one
can foresee a landscape, including human population patterns and
human-induced structures, which could look very different from what it
is now (Figure 1). Could we predict this? What will be the role of



1930

1980

2030 (projected)

Irrigation moving
upstream 

Irrigation moving
downstream 

Figure 1. Schematic of the evolution of the spatial patterns of
irrigation (shaded area) in the Murrumbidgee system (84,000 km²),
Southeast Australia. In the early 20th century, irrigation moved
upstream. Recently, the government has started buying water rights
from farmers to protect the environment. Panel 3 is one projection
that is based on the possibility of cutting back irrigation upstream.

M. SIVAPALAN, H. H. G. SAVENIJE AND G. BLÖSCHL
hydrology in any changes in the landscape including
societal changes, and in return, what will be the impact
of the societal changes on water cycle dynamics?
Should such predictions be the business of hydrologists
or social scientists? The common history of hydrology
and the societal changes seen in the Murrumbidgee is
an example of unexpected process dynamics. With
such dramatic changes to the landscape, prediction of
water cycle dynamics over long timescales is not
feasible without including the interactions and feed-
backs with human systems.

Welcome to socio-hydrology, the science of people
and water, a new science that is aimed at under-
standing the dynamics and co-evolution of coupled
human-water systems. As pointed out in a recent
editorial in the Economist magazine (see below),
natural scientists have for too long ignored the human
factor. Hydrologists are not exceptions to this. In
traditional hydrology, human-induced water resources
management activities are prescribed as external
forcings in the water cycle dynamics, under the
assumption of stationarity (Milly et al., 2008; Peel
and Blöschl, 2011). In socio-hydrology, humans and
their actions are considered part and parcel of water
cycle dynamics, and the aim is to predict the dynamics
of both.

“Too many natural scientists embrace the comforting
assumption that nature can be studied, indeed should be
studied, in isolation from the human world, with people
as mere observers. Many environmentalists—especially
those in the American tradition inspired by Henry David
Thoreau—believe that “in wilderness is the preservation
Copyright © 2011 John Wiley & Sons, Ltd.
of the world”. But the wilderness, for good or ill, is
increasingly irrelevant.” – Editorial in the Economist,
May 26, 2011

But what of the science of integrated water resources
management (IWRM), which has been around for a
long time, and is also clearly, and strongly, about people
and water. In what way is socio-hydrology different
from IWRM? A typical question addressed in IWRM
is: in what way does a management decision affect
runoff and, conversely, in what way is management
constrained by runoff? IWRM is also about interac-
tions of humans and water, and often uses the ‘scenario-
based’ approach as the common means to explore these
interactions (Savenije and Van der Zaag, 2008).
However, this approach may be unrealistic, especially
for long-term predictions, as it does not account for the
dynamics of the interactions between water and people.
For example, it is unlikely that the coupled system
dynamics of the Murrumbidgee basin, as reported
above, could have been predicted by a ‘scenario-based’
approach that does not account for the co-evolutionary
dynamics of coupled human-water systems, including
spontaneous or unexpected behaviours, as illustrated in
Figure 1. Hence, whereas the focus of IWRM is on
controlling or managing the water system to reach
desired outcomes for society and the environment, the
focus of socio-hydrology is on observing, understanding
and predicting future trajectories of co-evolution of
coupled human-water systems. In this sense, one could
say that socio-hydrology is the fundamental science
underpinning the practice of IWRM.
There is considerable similarity between the proposed

new science of socio-hydrology and the now established
field of eco-hydrology. Eco-hydrology explores the co-
evolution and self-organisation of vegetation in the
landscape in relation to water availability (Eagleson,
1982, 2002; Rodriguez-Iturbe, 2000; Berry et al., 2005).
Socio-hydrology, on the other hand, explores the co-
evolution and self-organisation of people in the landscape,
also with respect to water availability. We believe that
socio-hydrology stands to learn a lot from the success of
eco-hydrology, which has added new life to hydrology
through introduction of the concepts of co-evolution and
optimality that have previously been foreign to hydrology.
The introduction of eco-hydrology has helped spawn new
connections between hydrology and neighbouring
disciplines such as pedology, plant physiology and
geomorphology, and in this way it has helped to expand
the horizons of hydrology. In the same way, the advent of
socio-hydrology could also lead to a similar broadening of
the science, extending into the social sciences. However,
even while socio-hydrology will take on increasing
importance in the context of a changing, human-
dominated world, its practice may turn out to be more
challenging than eco-hydrology. This is because humans
Hydrol. Process. (2011)



INVITED COMMENTARY
possess more powerful ways and means of controlling
water cycle dynamics beyond the optimality, adaptation
and acclimation strategies that natural vegetation pos-
sesses and has developed over time.
Finally, the timing is just right for the launch of socio-

hydrology, as a new interdisciplinary but quantitative
science of people and water, with the ambition to make
predictions of water cycle dynamics, and thus underpin
sustainable water management. At a time when hydrol-
ogy textbooks continue to dwell on the complexities of
processes occurring in undisturbed places or under
idealized conditions, which are the exception rather than
the rule in the real world, and almost all water bodies are
affected by people in one way or another, there is an
urgent need for hydrology itself to adapt and evolve to
cope with the emergent scientific and practical challenges
in a changing world (Wagener et al., 2010), and prevent
and resolve conflicts between humans and the environ-
ment, and amongst humans themselves (Postel, 2011;
Koutsoyiannis, 2011). Socio-hydrology addresses this
strongly felt need. In fact, there have already been
several early attempts at exploring the co-evolution of
human-water systems. For example, Geels (2005) studied
the trajectories of co-evolution of water technology and
society in present-day Netherlands. Kallis (2010) studied
the co-evolution of water resource development in
ancient Athens. Pataki et al. (2011) have provided an
outline of the interplay of sociological and ecological
processes in urban water management.
EMERGENT DYNAMICS ACROSS SPACE
AND TIME
The essence of socio-hydrology, the point of departure
from IWRM, is, as mentioned before, the study of the
Figure 2. Precipitation shed of the Sahel (yellow contour). The scale indi
growing season, in absolute terms. Hence, from each pixel in the black
Sahel during the growing season. This has to be multiplied by the ratio o

the contribution to the rainfall in the target are

Copyright © 2011 John Wiley & Sons, Ltd.
co-evolution of humans and water on the landscape.
Winder et al. (2005) and Kallis (2007) have pointed out
that for a system to be considered co-evolutionary,
there must be a process of generation of ‘new
variations’, as they called them. New variations, also
known as ‘emergent behaviour’, are brought about by
feedbacks between processes at a range of scales, and
may lead to exceedance of ‘tipping points’ through
which the systems may evolve into new, perhaps
previously unobserved, states. The Murrumbidgee
example is a case in point.
In the Murrumbidgee basin, the spatial patterns of

organisation arising from co-evolutionary dynamics are
nevertheless underpinned by a directed stream net-
work. This is often the case; water abstraction
upstream will invariably affect people living down-
stream, and so will changes to water quality. However,
one can think of cases where such connections and
feedbacks are less obvious. The Sahel drought in the
1980s led to widespread famine and involuntary human
migration. One of the compounding factors that
contributed to the drought was land use change in
upwind areas (i.e. East Africa), leading to reduced
moisture cycling westward, and the consequent reduc-
tion of precipitation locally. The nature of moisture
recycling that contributed to drought in the Sahel is
illustrated in Figure 2, which was obtained by analysing
10 years of re-analysis data on global water circulation
(Van der Ent et al., 2010; Van der Ent and Savenije,
2011), and shows that 60% of the rainfall in the Sahel is
derived from terrestrial evaporation upwind (see
Figure 2). Reduction in moisture recycling from upwind
can introduce a positive feedback locally, with the
reduced precipitation leading to overgrazing, which
then leads to lower evaporation, which in turn leads to
cates how much each coloured region contributes to the rainfall in the
region, 25–30 mm of the evaporation contributes to the rainfall in the
f the contributing area to the target area (the yellow contour) to obtain
a (personal communication by Van der Ent).

Hydrol. Process. (2011)



M. SIVAPALAN, H. H. G. SAVENIJE AND G. BLÖSCHL
still lower precipitation. The Sahel example is one
where, rather than being affected by human activities
upstream, the water cycle is affected by human activities
upwind. Consequently, instead of having to deal with a
‘watershed’, we now have to deal with a ‘precipitation
shed’. The critical issue facing socio-hydrology is that
the local people are powerless to affect the ‘precipita-
tion shed’. How could people in the Sahel seek local
solutions outside of the watershed? The traditional way
under such circumstances is via food imports. Unfor-
tunately, war and conquest tend to be other unintended
consequences. This is an example of the primary
challenges of the new field of socio-hydrology.

As mentioned before, while eco-hydrology studies
how vegetation organises itself in the landscape with
respect to water, socio-hydrology studies how people
organise themselves in the landscape with respect to
water. Ancient human settlements were mostly orga-
nised along streams, which they used as a means of
transport and water supply, and therefore access and
proximity to water courses or sources governed the
primary human settlement patterns. With increasing
technological capability, humans could manage to settle
away from streams and access water through recourse
to technology and to use alternative means for
transport. Therefore, just as eco-hydrology aims to
learn from vegetation patterns and their evolution,
socio-hydrology can potentially learn from human
settlement patterns, through interpreting them in terms
of access and proximity to water resources and socio-
economic and technological factors impacting differen-
tially on these in different parts of the world. In other
words, there are many parallels between eco-hydrology
and socio-hydrology, even as there are substantial
differences.

An important feature of non-linear systems is that
fast processes interact with slow processes to produce
complex and rich dynamics. For example, these
interactions may lead to exceedance of critical thresh-
olds or tipping points. Resilient social-ecological
systems are those that continually change and adapt
yet remain within critical thresholds (Folke et al., 2010).
Climatic, hydrological and societal drivers often appear
as shocks (floods, droughts, wars, economic collapse)
and may push the system beyond these resilience
thresholds. In a hydrological landscape such as the
Sahel, resilience may be low, so change to a different
mode – e.g. desertification, famine and human migra-
tion in the case of the Sahel – may occur more readily
(Folke et al., 2004). On the other hand, in temperate
climates the resilience thresholds tend to be higher. But
even in relatively wet regions, unexpected changes of
the system may yet occur. For example, the traditional
source of drinking water in Bangladesh used to be rain-
fed ponds. When the community switched to groundwater
as a source of water supply in the 1980s, responding to the
Copyright © 2011 John Wiley & Sons, Ltd.
contamination of the ponds by pathogens, there was not
the expectation that the pumping would lead to arsenic
mobilisation and widespread poisoning.
In classical hydrology, feedbacks across space and

time scales are very important (Blöschl, 2001; Merz and
Blöschl, 2008; Montanari et al., 2010), but due to non-
linear feedbacks with human activities, the socio-
hydrologic system has the tendency to lead to surprises
(Gordon et al., 2008), otherwise known as Black Swan
events (Taleb, 2007), which therefore make predictions
a real challenge. A better understanding of the
resilience thresholds and the likelihood for surprises
may assist in management decision making by account-
ing for wider process dynamics (Kumar, 2011). As
socio-hydrology is concerned with longer term dynam-
ics, predicting possible trajectories of the system
dynamics are of most interest to governments who are
faced with making strategic, long term-decisions.
DRIVERS OF SOCIO-HYDROLOGIC PROCESSES
An important part of understanding socio-hydrologic
processes is to understand which way the water is flowing
and why this is so. In subsurface hydrology, the main
driver of flow and transport is a potential gradient.
Streams flow in response to topographic gradients, and
evaporation occurs due to humidity gradients. In socio-
hydrology there is a wider range of controls related to the
interplay of socio-economic and hydrologic processes at a
range of scales. For example, water flows downhill except
in the case of diversions when it can be pumped uphill. The
pumping is the social component and demonstrates that
social factors can be a powerful force. An example of flows
that socio-hydrology might address is the so-called ‘virtual
water trade’. Figure 3 illustrates the fluxes of virtual water
along shipping lanes in relation to wheat. Virtual water
refers to the amount of water needed to produce food (or
other commodities), which is then transported to the place
of consumption (Chapagain et al., 2006; Mekonnen and
Hoekstra, 2010; Koutsoyiannis, 2011). The gradients that
drive the flow of virtual water tend to be differences in
policies, subsidies, economic incentives, technologies, fuel
costs and historical factors. Trade barriers also play a role.
In principle, one could argue that the flows should be from
regions that are water abundant and produce more
efficiently in respect of water use to those that have
less access to fresh water and produce less efficiently
with respect to water use. Increasingly, however,
policies and markets tend to be the main drivers. For
example, the world food market is increasingly
controlled by multinationals, retailers, supermarkets
and powerful countries. The interplay of these global
interests with the temporal and spatial variations of
the water resources at the local level, which are often
the determining factors for water scarcity, leads to
complex systems dynamics (Savenije, 2000).
Hydrol. Process. (2011)



Figure 3. National virtual water balances and net virtual water flows related to trade in wheat products in the period 1996–2005. Only the
largest net flows (>2Gm³/year) are shown (taken from Mekonnen and Hoekstra, 2010).

INVITED COMMENTARY
Socio-hydrology is therefore concerned with analys-
ing the following why questions: What drives this
system (for example, as a part of the international trade
of food)? What are the fluxes, what are the gradients
and can they be related? But quantity of water is not
the only factor; water quality may be equally or even
more important, in particular in water-rich countries.
The European Water Framework Directive and the
Clean Water Act in the US have both led to a major
wave of human actions. Non-consumptive water trans-
fers (such as water use in industry and households)
often change the quality or reduce the opportunity for
beneficial use both in terms of location and quality. In
particular, this reduces the opportunities for other
functional uses, or ecosystem services. For example, the
food industry in Holland uses imported food from
Brazil (soybean, tapioca) for pork production. This is
tantamount to the import of nutrients from Brazil
(which itself is nutrient poor) and its transport to the
Netherlands (which has a nutrient rich environment).
The resulting financial profit is not in balance with the
environmental harm that such imports cause. Further-
more, there is a perverse incentive introduced by the
fact that the environmental costs are not charged to the
consumer. An interesting socio-hydrologic challenge will
be how virtual water flows will change and co-evolve if
taxes were placed on the virtual water trade.

SOCIO-HYDROLOGY: THE WAY FORWARD
We argue in this paper for a new science of socio-
hydrology that treats people as an endogenous part of the
water cycle, interacting with the system in multiple ways,
including through water consumption for food, energy
and drinking water supply, through pollution of fresh-
water resources, and through policies, markets, and
technology. What sets socio-hydrology apart from IWRM
is that socio-hydrology explicitly studies the co-evolution
Copyright © 2011 John Wiley & Sons, Ltd.
of humans and water. It explores the way the coupled
human-water system evolves and possible trajectories of
its co-evolution, including the possibility of generating
emergent, even unexpected, behaviours. Socio-hydrology
is aimed as a discovery-based fundamental science, whose
practice is informed through observing, understanding
and predicting socio-hydrologic phenomena in real places
in the landscape where real people live. Socio-hydrology
will also have to accommodate the time arrow by focusing
on longer time scales including on dynamics we never had
to deal with. We insist, however, that socio-hydrology
must strive to be a quantitative science. While broad
narratives may be important for context, quantitative
descriptions are needed for testing hypotheses, for
modelling the system and for predicting possible future
trajectories of system states.
What is the way forward in socio-hydrology? We

believe there are at least three avenues through which
socio-hydrology can advance:

1. Historical socio-hydrology: First and foremost, we
can learn from reconstructing and studying the past,
both in the immediate past, and in the distant past.
Indeed, water has played a key role in the growth,
evolution and eventual collapse of numerous ancient
(and not so ancient) civilisations. The collapse of the
Sumerian civilisation has been attributed to rising
water tables and salinisation as a result of extensive
irrigation (Ponting, 1991). Apart from collapse of
civilisations, interesting patterns of water governance
and technologies have evolved throughout history.
For example, Iran saw the development and evolu-
tion of ‘Qanats’, sloping tunnels that tap into the
groundwater without the need for pumping, which
have survived the test of time over millennia.

2. Comparative socio-hydrology: Sivapalan (2009,
p.1395) has suggested that ‘. . . instead of attempting
to reproduce the response of individual catchments,
Hydrol. Process. (2011)



M. SIVAPALAN, H. H. G. SAVENIJE AND G. BLÖSCHL
research should advance comparative hydrology,
aiming to characterize and learn from the similarities
and differences between catchments in different
places, and interpret these in terms of underlying
climate-landscape-human controls.’ In the context of
socio-hydrology, this implies a comparative analysis
of human-water interactions across socio-economic
gradients, as well as climatic and other gradients, to
map any spatial or regional differences back to
processes and their temporal dynamics (Blöschl et al.,
2007; Wagener et al., 2010; Peel and Blöschl, 2011).

3. Process socio-hydrology: To complement the temporal
and spatial analyses, it would be of interest to study a
small number of human-water systems in more detail,
including routine monitoring, to gain more detailed
insights into causal relationships. This may involve
detailed data collection of the hydrological and
sociological processes involved, including real-time
learning, to understand human-water system functions
in the present to be able to predict possible trajectories
in the future. To make headway in the new science, we
need new scientific laws at the scales of interest, but
particularly dealing with human-nature interactions.
Examples of such laws are flux-gradient relationships,
which have served classical hydrology well in many
ways. Since socio-hydrology is about co-evolution and
feedbacks operating at multiple scales, the notions of
optimality and goal functions are likely to be important
and useful, just as they have been in eco-hydrology
(Schymanski et al., 2009; Schaefli et al., 2011).

The important feature in all three areas of enquiry, to
reiterate, is the focus on co-evolution and emergent
patterns, including the unexpected, which are the main
points of departure from the recourse to scenario
analyses that is common in IWRM. With the advent of
socio-hydrology, the way we will do our science, as well
as the way we teach, will be different as humans begin to
play a much bigger role in water cycle dynamics. Just as
in the case of eco-hydrology, there will be a need for new
partnerships that go beyond our usual networks. As
socio-hydrology embraces processes beyond purely
physical (or biological) relationships, Sivapalan’s (2005)
call for a paradigm shift towards more holistic descrip-
tions and process interactions may become critically
important. All of these point to both challenging and
exciting times for the future of hydrologic science.
ACKNOWLEDGEMENTS
This paper is a part contribution of the NSF-funded
Hydrologic Synthesis Project: Water Cycle Dynamics in
a Changing Environment: Advancing Hydrologic
Science through Synthesis (NSF Grant EAR-0636043).
We would also like to thank Austrian Science Funds
(FWF) project DK-plus W1219-N22 for their financial
Copyright © 2011 John Wiley & Sons, Ltd.
support. The paper benefited from interactions with
several people, including Sally Thompson, Ciaran
Harman, Thorsten Wagener, Alberto Montanari, Saket
Pande, Larry Band, Amit Chanan, Jaya Kandasamy
and Vigi Vigneswaran. We are grateful for their
valuable contributions to our thoughts on the subject.
Special thanks to Michael Roderick for many insightful
comments, which reminded us that we have only
scratched the surface of a complex challenge. The
paper also benefited from critical review comments by
Demetris Koutsoyiannis.
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