Threats and Impacts to Groundwater- Dependent Wetlands Doñana, Spain

Threats and Impacts to Groundwater- Dependent Wetlands Doñana, Spain

Marisol Manzano and Emilio Custodio

Dept. Geotechnical Engineering, Technical University of Catalonia,

UPC Campus, Barcelona, Spain

CONTENT

1. Geographical location and geology of Doñana aquifer

2. Main environmental, social and economical aspects

3. Environmental impacts of intensive and localised groundwater exploitation

4. Towards a sustainable use of groundwater and the environment.

5. Conclusions

- SW Spain, between Sevilla, Huelva and Cádiz.

- Right bank of the Guadalquivir river at its estuary on the Atlantic Ocean

1. Geographical location and geology

PLIO-QUATERNARY ≈ Doñana aquifer Marsh Unit: clay

Eolian Unit: sand

Guadiamar river terraces

Deltaic Unit: sand and silt Alluvial Unit: sand and gravel

Lagoon Town River

UTM (km)

SEVILLA

4140

4100

710 750

HUELVA

marshes

RIVER

La Rocina

TINTO RIVER

Erased

El Rocío

dunes

Activ e dun

es

Aquifer extent:

aprox. 3600 km²

Doñana National Park: 54251 ha Peripheral buffer zone: 26540 ha Doñana Natural Park: 55377 ha Total protected surface: 136168 ha

CÁDIZ

- Plio-Quaternary sand, silt and gravels.

- Quaternary sand sheets, shifting dunes and clay marshes

2a. Main environmental aspects

¾ Great diversity of biotopes, especially lagoons, marshlands, fixed and mobile dunes, scrub woodland and pine forest.

¾ Habitat of: 875 plant species; 365 bird species; amphibious; fishes;

mammals,…

¾ Home of threatened species (Aguila Imperial, Lince,…) and Europe’s largest winter habitat for migrating birds (> 6 M birds/year)

¾ 1969: Creation of Doñana National Park

¾ 1981: Biosphere Reserve (UNESCO-MAB)

¾ 1982: RAMSAR Site (Humid zone of Int. Importance)

¾ 1994: Natural World Heritage Site

2b. Main environmental aspects

AUGUST 1985

Main patterns of groundwater-dependent wetlands in Doñana

GROUNDWATER DISCHARGE TO DEPRESSIONS AND CREEKS

Permanent groundwater discharge to ponds

precipitation evapotranspiration

evaporation

water table

precipitation evapotranspiration

stream flow generation

Permanent stream generation

water table Buffer to (some) pollutants

Wet season

or year

precipitation

Seasonal / interannual groundwater discharge

wet year/season water table

dry year/season water table Soil erosion and transport

Pollutants

precipitation

evapotranspiration

stream flow

Seasonal/interannual stream generation

water table Soil erosion and transport

Pollutants

Dry season

or year

3a. Hydrological impacts of intensive groundwater exploitation

REGIONAL PIEZOMETRY

October 1972 October 1996

UNDISTURBED SITUATION DISTURBED BY INTENSE PUMPING

-20

Location of main pumping sites

Location of main pumping sites

Guadalquivir river

b

-12 -8 -4 0 4

1970 1975 1980

-2 0 2 4

0 50 100 150 200 250 300 350

Days after 01/01/1970

0 4 8 12 16

1970 1975 1980

0 10 20

1970 1975 1980

Time (years)

Elevation(m.a.s.l.) m.a.s.l.

MAIN FEATURES

1. Phreatic level close to soil surface most of the year.

2. Groundwater discharges through:

• phreatic transpiration (phreatophytes)

• springs and seepage to small streams and ponds

• evaporation from the soil 3. Wetlands are abundant,

mostly permanent 4. Riparian areas: buffer

zones attenuating NO₃ in discharging polluted

ground-water

La Rocina ravine andriparianforest Active spring

or ravine Rainfall (Recharge)

Silt (∼impervious) Gravel Sand

NATURAL FLOW:

UNDISTURBED SITUATION

Phreatic level

Deep piezometric level

Phreatic transpiration

Well or borehole screen

Groundwater flow path

W E

3b. Environmental impact of intensive groundwater exploitation

La Rocina ravine andriparianforest La Rocina ravine

Active spring or ravine

Dry spring or ravine

Groundwater pumping Groundwater

pumping Rainfall (Recharge)

Silt (∼impervious) Gravel

Sand

NATURAL FLOW:

UNDISTURBED SITUATION

FLOW DISTURBED BY GROUNDWATER PUMPING

Phreatic level

Deep piezometric level

Phreatic transpiration

Well or borehole screen

Groundwater flow path

MAIN FEATURES

1. Phreatic level close to soil surface most of the year.

2. Groundwater discharges through:

• phreatic transpiration (phreatophytes)

• springs and seepage to small streams and ponds

• evaporation from the soil 3. Wetlands are abundant,

mostly permanent 4. Riparian areas: buffer

zones attenuating NO₃ in discharging polluted

ground-water

W E

La Rocina ravine andriparianforest La Rocina ravine

Active spring or ravine

Dry spring or ravine

Groundwater pumping Groundwater

pumping Rainfall (Recharge)

Silt (∼impervious) Gravel

Sand

NATURAL FLOW:

UNDISTURBED SITUATION

FLOW DISTURBED BY GROUNDWATER PUMPING

Phreatic level

Deep piezometric level

Phreatic transpiration

Well or borehole screen

Groundwater flow path

MAIN FEATURES

1. Depletion of phreatic and piezometric levels, causing:

• riparian / phreatophyte vegetation to disappear

• springs, diffuse discharge and small ravines may

disappear

• enhanced erosion and sediment transport

• wetlands inundation frequency and lasting

decrease (some disappear) 2. Wetland surface decrease 3. Pollutants (nutrients) more

persistent, spreading deeper and wider

W E

Other significative Threats and Impacts on the Doñana wetlands

DEFORESTATION

• Induced erosion and sedimentation

• Humid surface decreases by progressive filling up of small depressions and marshes

WATER AND SOIL POINT AND DIFFUSE

CONTAMINATION

•Sources: * agrochemical (nutrients, pesticides)

* industrial (oil/wine wastes, pig slurry)

* urban (untreated sewage)

• Progressive water quality (ecological) deterioration

• Centimetric-range water table lowering because of increased evapotranspiration

• Decrease of humid surface by reducing the

phreatic discharge to soil surface and vegetation

INTRODUCTION OF HIGH WATER-

DEMANDING VEGETATION (EUCALYPTUS)

5. Conclusions

Doñana holds hundreds of wetlands with different

geomorphic and hydrological pattern. Most of them are directly related to groundwater:

- Groundwater is the main contributor to many environ- mental, economical and social goods & services in Doñana

1.

Intensive groundwater abstraction during 35 years modified many wetland's natural hydrological pattern:

- Pumping (concentrated in aquifer discharge areas)

converted permanent wetlands into temporal or sporadic, and many sporadic ones disappeared.

- Many small ravines converted from lineal phreatic

discharge zones into irrigation excess collectors; they are jeopardised by nutrients and pesticides.

2.

5. Conclusions (2)

Uncontrolled deforestation for 40-50 years favoured sand mobilisation and relocation:

- Small seasonal wetlands were filled up and disappeared.

3.

Eucalyptus (introduced 50 years ago) induced a local increase of the evapotranspirative phreatic discharge:

- Produced a 0.5 - 1 m water-table decline that changed the hydrological pattern of some wetlands (permanent converted into seasonal or sporadic; other disappeared).

4.

Restoration of wetlands natural performance requires to restore the aquifer hydraulic balance:

- Decreasing abstracted volumes and re-location of wells.

5.