Presentation at Aguas2009, November 2009, Cali, Colombia. Mark Mulligan.

1. The human footprint on water :
agricultural, industrial, and urban
impacts on the quality of available
water globally and in the Andean
region
Mark Mulligan, King’s College London,
UNEP-WCMC
mark.mulligan@kcl.ac.uk
[30 mins]

2. The issue
• Land use and cover change affects hydrological processes
and thus downstream users of water
• With increasing populations and human appropriation of
land careful management of these impacts is necessary
• PES schemes are one mechanism by which downstream
beneficiaries can pay upstream land managers for the
hydrological services provided
• The hydrological services considered are generally water
quantity, flow regulation and water quality
• Whilst there are reasonable data and spatial models for
water quantity and flow regulation (in part because of the
availability of remotely sensed data...
• Spatial water quality data and models are much less
developed

3. Rules of thumb for the water service benefits of ‘protected’ areas
Water quantity services
•Protected ecosystems do not necessarily generate more
rainfall than agricultural land uses.
•Protected ecosystems may have higher evapotranspiration
and thus lower water yields
Thus quantity benefits difficult to prove
Water regulation services
•Protected ecosystems do not protect against the most destructive
floods
•For ‘normal’ events they do encourage more subsurface flow and
thus more seasonally regular flow regimes
Likely benefits especially in highly seasonal environments
Water quality services (quantity for a purpose)
•Protected ecosystems encourage infiltration leading to lower soil
erosion and sedimentation
•Unprotected land will tend to have higher inputs of pesticides,
herbicides, fertilisers ...
Clear benefits of PA’s: generation of higher quality water than non-
protected areas

4. Quality determines quantity
1. Water quality = water availability (for a
purpose)
2. Quantity and access can be high but if
quality is not sufficient then water
scarcity can still exist
3. Countries like Colombia have a lot of
water but to what extent is it all usable
without expensive water treatment?

5. Q. How can we understand the impact of human activity on water
quality when water quality cannot be assessed from remote
sensing?
A1. identify the proportion of your water originating in upstream
protected areas
A2. Identify the point and non point sources and calculate the
‘upstream human influence’ on river water

6. Protected areas : nature’s water filter
•12-14% of the terrestrial
surface is nominally protected
•34% of ice free areas are used
for agriculture and grazing
•The rest is ice, desert,urban or
unprotected wilderness
•Mean management budget:
$8.75 per km2* 1872
*estimated on the basis of James, A.N., Green, M.J.B. and Paine, J.R. 1999. A Global Review
of Protected Area Budgets and Staffing. WCMC – World Conservation Press, Cambridge, UK. vi + 46pp

7. Quantifying the hydrological value of global protected areas
Protected areas may help with water quantity and regulation functions and
certainly help with water quality functions.
Protected areas provide a ‘purification function’ on the basis that they tend to
have lower human influence on water.
Assumption:
Water draining from a protected area is better (higher quality, better regulated)
than water that drains from non-protected areas
Method
1. Combine global rainfall dataset (1km resolution) with global dataset of flow directions (Hydro1k,
HydroSheds)
2. Route rainfall down the flow network
3. For each pixel downstream calculate the proportion of runoff in that pixel derived from protected
areas upstream
4. Combine with population and urban areas datasets (CIESIN) and calculate the number of persons
benefitting from runoff originating in protected areas
5. Put online in Google maps/Earth : see http://www.kcl.ac.uk/geodata
6. Repeat for other ‘contributing’ areas (forests, mountain forests, non-protected but non-
agricultural areas etc.)

8. % of water originating in a protected area – WDPA 2009 (Colombia) [gl_pc_wc_fin]
Protected areas provide a
‘purification function’ on the basis
that they tend to have lower
human influence on water.
As you travel downstream
from the protected areas their
contribution to flow diminishes as
rivers are swamped with water
from non-protected areas
see www.kcl.ac.uk/geodata

9. Modelling the human footprint on water
0.1*Pr 1.0*Pm P non-human-influenced
Frac*Pa
Frac*Pg 1.0*Pog
1.0*Pu
P non-human-influenced Frac*Pc
Human Footprint on Water=∑Ppolluting /∑Ptotal

10. Roads Mines
Point sources
Urban areas Oil and gas

11. Pasture Cropland
Non-point sources
+
Protected areas Unprotected agriculture
- =

12. % of water that is human impacted
At the global scale dominated by the human agricultural footprint

13. % of water that is human impacted
At the continental scale the
influence of roads and
protected areas becomes
more obvious

14. % of water that is human impacted
At the national scale the
downstream decay of
influence away from
agricultural and urban areas is
clearer.
We might expect the human
influence to be reflected in
higher sediment loads,
organic and inorganic
contaminants, incl. pesticides
and fertiliser etc.
This decay results from the
dilution of human influenced
water with runoff from less
influenced areas.

15. % of water that is human impacted
At the regional scale the distance
decay is clear with some rivers still
being 25% influenced by upstream
polluting activities some 150 km
downstream.
The extent of the influence depends
on the area of the polluting activity
(though in reality the intensity of
pollution will also be important.
Protected areas ‘purify’ through
dilution
Oil wells may have a locally intense
influence but it is soon diluted and
fades quickly
Takes no account of exposure levels :
a measure of influence not of
toxicity

16. % of water that is human impacted
(transparent=negligible influence)
The human footprint on water is
concentrated around human
populations (roads, agric, industry,
urban tend to coalesce).
Thus around major cities water
quality could be heavily influenced
Strategic positioning of protected
areas can have positive impacts on
the water supply of urban areas

17. % of water supply to urban areas that is human impacted
At the local scale supply to urban areas is influenced by water diversions,
aqueducts, transfers etc. for which there are no data globally.
But, if we assume that rivers running into urban areas supply those areas with
water then we can map the heavily impacted urbanisations
Many of these cities will use intensive water treatment to offset these impacts

18. % of water supply to urban
areas that is human
impacted
Although Colombia has a lot of
water it also has high
population, large urbanisation
and intensive agriculture in the
Andes.
Colombia’s urban water supplies
are thus heavily influenced by
upstream human activity
This necessitates costly
diversion schemes or water
treatment.
Putting a natural PA buffer
between populations and the
mess they create can deliver
clear water quality benefits at
low cost.

19. Thank you
Questions?

21. % of water supply to urban
areas that is human
impacted

22. Methods
1. Map global distribution of threat factors (1km spatial resolution GIS database) for
point and non point sources
2. Integrate global maps of water inputs i.e. Rainfall (from WorldClim and TRMM)
3. Integrate global maps of flow directions (Hydro1k, Hydrosheds)
4. Calculate influence of each upstream point and non-point source as :
Area of point source polluting activities+ = (mines + oilandgas + roads++*0.1 + urban)
Area of unprotected agricultural land+ = (pasture + cropland) * (1-protected)
Total polluting area per pixel (P) = max (1.0, point source polluting activities,
unprotected agricultural land)
These were summed downstream along the flow network top give Pd
The rainfall (Rf) falling on all areas was also calculated and summed downstream to
give Rfd.
Human influence (%) = (Pd/Rfd) * 100 (the percentage of flow in a given pixel that fell
as rain on an upstream human influenced area: a measure of the potential
upstream influences on water quality).
+Mines= mine according to Hearn et al. (2003), Oilandgas = oil and gas field according to Hearn et al. (2003) (binary), Roads = roads (binary), Urban = urban
area according to CIESIN et al. (2004) (binary), Pasture = pasture land according to Ramankutty et al. (2008), Cropland = cropland according to
Ramankutty et al. (2008), Protected= nationally or internationally protected areas according to WDPA (2009) (binary).
++ roads , if present, are assumed to occupy 10% of the pixel area