STUDY SITE 5: Messara Valley, Crete, Greece
- Published: Monday, 16 January 2012 15:09
- Written by Joost Vlaming (SU)
Responsible partner: TUC
1. General information
The rapid development of Crete in the last 30 years has exerted strong pressures on many sectors of the region. The growth of agriculture in the Messara plain has strong impact on the water resources and ecosystem services of the area by substantially increasing of water demand. The economy of the region is based on agriculture with intensive cultivation mainly olive trees, grapes, citrus, and vegetables in green houses.
2. Geographical description
The Messara basin encompasses an area of 611 km2 located in the central-south area of Crete (Figure 6.5) and extends into two catchments. The topography is a typical of a graben formation and the surface drops within 15 km from 2,454 to 45 m asl. The plain area of two catchments hosts the largest alluvium aquifer system of the island, extended in an area of 216 km2.
Figure Location of Messara basin.
3. Main ecosystem(s) in the study area and functions/services they provide
About 250 km2 of the total Valley area are cultivated and the remaining area (higher grounds) is used for livestock. The main land-use activities are olive growing (Figure 6.6) and grape vine cultivation. The remainder of the cultivated land is used for vegetable, fruit and cereal growing. The Messara Valley has remained rural with a small population of about 40.000 inhabitants. The main source of irrigation and domestic supply is groundwater. The Messara Valley is classified as dry sub-humid according to UNCED (Paris Convention on Desertification, 1994) definitions.
Figure Messara Valley - olive growing activities. View from Phaistos (outlet of the valley). Areal photo of the Faneromeni Dam partially filled (August 2006).
4. Ecosystem dynamics – are there indications for irreversible change in the area, and that critical thresholds and tipping-points regulate such changes? And what are the drivers for change?
Experts assess that the Messara Valley is threatened with desertification. Figure 6.7 shows evidence of the dramatic drop of more than 30m in the mean groundwater level during the period 1989-2002. The depletion of the aquifer has reduced water availability as groundwater is a major resource for irrigation. The causes can be traced in the uncontrolled pumping and use and this has created tension amongst the users. The groundwater level dropdown started with the introduction of pumping of the groundwater store for drip-irrigation of the main crop which is olive trees.
Figure (a) left: Seasonal Data from 3 wells in the Messara aquifer, (b) right: Simulated extent of seawater intrusion into the Tymbaki aquifer at various depths
The impact of groundwater abstraction on the ecosystem of the watershed became obvious when the springs in the surrounding hills dried up and the natural flora and fauna of the environment around these springs perished, with the loss of birds, small animals and flowers. The wetlands of the Messara Plain were once known for the large number of waterfowl and wild ducks. The Geropotamos Stream was known for its large eel population, and its banks for their significant wild rabbit and hare populations. These populations are now almost extinct, partly due to the drying up of the wetlands and partly due to agricultural pesticide poisoning. There is some concern by land ecologists that African plant species might be replacing the native Aegean species in the Valley. The wetlands have virtually disappeared. Olive mill slurries discharged into the streambeds during the winter months are becoming a major concern, as they are toxic and are infiltrating into the aquifer system. There has been some discussion about using oil mill wastes for some other purpose in order to stop them being dumped into the streams. Another problem is that the stream channels are often used as dumps for rubbish, including plastic. Waste trucks are also using the riverbed as a dumping ground. The aquifer of the 50 km2 coastal Tymbaki basin consists of Pleistocene to Holocene alluvial deposits and is block faulted by post Upper Pleistocene normal faults. Simulation of seawater intrusion, has established that at the southern end of the coast, by the Geropotamos river alluvial recharge zone, the toe of the saltwater intrusion front lies 550 to 600 m from the coastline. At the northern end of the coast, the toe of the saltwater intrusion front is located 1500 m from the coastline. The Geropotamos river is by the far the most important water supplier to the Tymbaki aquifer and as such, regulates both seawater intrusion extent and pattern.
5. Relevant end-users of knowledge in the region / country (like natural resource and biodiversity managers, local/regional/national authorities, users or beneficiaries of ecosystem services
- Directorate of Agriculture Development, Region of Crete
- Directorate of Environmental and Spatial Planning, Region of Crete
- Directorate of Water Resources Management, Region of Crete
- Directorate of Regional Forestry, Region of Crete
- Directorate of Civil Protection, Region of Crete
- Local municipal departments
6. Past and on-going projects on ecosystem functioning, thresholds, and related aspects
- FAO. 1972c Overall Study of the Messara Plain. Report on Study of the Water Resources and their Exploitation for Irrigation in Eastern Crete. FAO Report No. AGL:SF/GRE/31.
- Dietrich G. and Kilakos J. 1971 Groundwater quality in the Messara Plain in Eastern Crete, Greece. Working Document No. 18. FAO/UNDP/AGL:SF/GRE 17.
- MESSARA , An integrated monitoring and modeling study of desertification and climatic change Impacts in the Messara Valley of Crete, ENVIRONMENT Program, EU, DG-XII, 1994-96
- Yassoglou N., 1971. A study of the soil of Messara valley in Crete, Greece. Greek Nuclear Research Centre, Athens, Greece.
- EU research project Grapes – Groundwater and River Resources Programme on a European Scale. Contract ENV4 – CT 95 – 0186, DG XII, February 1996
- National research project BEWARE - Best Water Use Innovative Practices towards a Sustainable Water Resources Management, (CRINNO) (2002-2005)
- MEDIS - SIMULATION OF SEAWATER INTRUSION INTO THE TYMBAKI AQUIFER, SOUTH CENTRAL CRETE, GREECE, Savvas N. Paritsis. (EVK1-CT-2001-00092(, (2002-2006)
- EU research project HarmoniRiB – Harmonised Techniques and Representative River Basin Data for Assessment and Use of Uncertainty Information in Integrated Water Management (EVK1-CT-2002-00109) (2002-2006).
- DESIRE FP6: Desertification mitigation and remediation of land - a global approach for local solutions. SUSTDEV-3 Global change and ecosystems,SUSTDEV-2005-3.IV.1.1, (2007-2012).
7. Key references about ecosystem dynamics in the study area or wider spatial setting
- Tsanis, I.K., Koutroulis A.G., Daliakopoulos, I.N., D. Jacob., “Severe Climate-Induced Water Shortage in Crete”, Climatic Change Letters, 2010 (submitted)
- Koutroulis A.G., Vrochidou A., Tsanis I.K., “Spatial and temporal characteristics of droughts for the island of Crete”, Journal of Hydrometeorology, 2010 (in press) doi: 10.1175/2010JHM1252.1.
- Tsanis I. K., P. Coulibaly, I. N. Daliakopoulos, 2008. Improving groundwater level forecasting with a feedforward neural network and linearly regressed projected precipitation. Journal of Hydroinformatics 10 (4) 317–330
- Daliakopoulos I. N., P. Coulibaly, I. K. Tsanis, 2005. Groundwater Level Forecasting Using Artificial Neural Networks, Journal of Hydrology, 309, 229 - 240
- FAO (1970) Study of the water resources and their exploitation for irrigation in eastern Crete – Greece. Overall study of Messara Plain AGL:SF/GRE 31 tech rep. 1, UNDP, Iraklio and Hydrology of the western Messara, AGL:SF/GRE 166 tech rep. 13, UNDP, Iraklio
- M. Kritsotakis, I.K. Tsanis, “An integrated approach for sustainable water resources management of Messara Basin, Crete, Greece”, EWRA, 27/28: 15-30, 2009
- Chartzoulakis, k, G. Psarras, Global change effects on crop photosynthesis and production in Mediterranean: the case of Crete, Greece, Agriculture, Ecosystems & Environment, 106 (2-3), 2005, pp. 147-157, DOI: 10.1016/j.agee.2004.10.004.
- Allen, HD, Randall RE, Amable, GS & Devereux BJ (2006) The impact of changing olive cultivation practices on the ground flora of olive groves in the Messara and Psiloritis regions, Crete, Greece Land Degradation & Development, 17, 249-273 doi:10.1002/ldr.716