The human footprint on water : agricultural, industrial, and urban impacts on the quality of available water globally and in the Andean region

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

[email protected][30 mins]

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

Water quantity services

•Protected ecosystems do not necessarily generate more rainfall than agricultural land uses.•Protected ecosystems may have higher evapotranspirationand thus lower water yieldsThus 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 regimesLikely 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

Rules of thumb for the water service benefits of ‘protected’ areas

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?

Quality determines quantity

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

•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*

Protected areas : nature’s water filter

*estimated on the basis of James, A.N., Green, M.J.B. and Paine, J.R. 1999. A Global Reviewof Protected Area Budgets and Staffing. WCMC – World Conservation Press, Cambridge, UK. vi + 46pp

1872

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

Method1. Combine global rainfall dataset (1km resolution) with global dataset of flow directions (Hydro1k,

HydroSheds)2. Route rainfall down the flow network3. For each pixel downstream calculate the proportion of runoff in that pixel derived from protected

areas upstream4. Combine with population and urban areas datasets (CIESIN) and calculate the number of persons

benefitting from runoff originating in protected areas5. Put online in Google maps/Earth : see http://www.kcl.ac.uk/geodata6. Repeat for other ‘contributing’ areas (forests, mountain forests, non-protected but non-

agricultural areas etc.)

% of water originating in a protected area – WDPA 2009 (Colombia) [gl_pc_wc_fin]

see www.kcl.ac.uk/geodata

Protected areas provide a ‘purification function’ on the basis that they tend to have lower human influence on water.

As you travel downstreamfrom the protected areas theircontribution to flow diminishes asrivers are swamped with water from non-protected areas

Modelling the human footprint on water

Frac*Pg 1.0*Pog

1.0*Pu

0.1*Pr 1.0*Pm

Frac*Pa

Human Footprint on Water=∑Ppolluting /∑Ptotal

Frac*PcP non-human-influenced

P non-human-influenced

Roads Mines

Urban areas Oil and gas

Point sources

Pasture

Unprotected agricultureProtected areas

Cropland Non-point sources

+

- =

% of water that is human impacted

At the global scale dominated by the human agricultural footprint

% of water that is human impacted

At the continental scale the influence of roads and protected areas becomes more obvious

% 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.

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 dilutionOil wells may have a locally intense influence but it is soon diluted and fades quicklyTakes no account of exposure levels : a measure of influence not of toxicity

% of water that is human impacted

% 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

% 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 urbanisationsMany of these cities will use intensive water treatment to offset these impacts

% 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.

Thank you

Questions?

% of water supply to urban areas that is human impacted

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 PdThe 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

Methods