Case Study experiment - Soil Salinization
1) Application of biological agents to increase crop resistance to salinityThe experiment tested the effectiveness of Trichoderma harzianum (a fungus) on tomato resistance to saline irrigation. This was a reference study (i.e. few samples but high stakeholder involvement) in order to provide reference for the experiment in a pilot study. The pilot study simulateed the experiment in a fully monitored greenhouse in TUC, Chania.
|Setting up the greenhouse experiment|
While T. harzianum successfully reduced the effect of higher salinity irrigation and positively affected bioavailable nutrients concentration in the soil, its effect was limited, especially on subsequent cropping seasons. Results showed that soil quality was significantly affected by the irrigation treatment, and production loss due to saline irrigation was substantial (21-38%), especially for the marketable fraction of yield. Also, from a point onward, the increased taste characteristics associated with higher salinity came at a high cost for both yield and soil health. Furthermore, 2nd year crops showed an even higher productivity risk even under improved irrigation water quality and soil salinity mitigation measures. Moreover, modelling results show that future conditions will worsen the situation for greenhouses that already face a high salinity problem, either by rendering production nonfeasible or by increasing water demand by as much as 25%.
2) Rainwater HarvestingThe Crete researchers also explored the cost-effectiveness of installing rainwater harvesting systems in greenhouses.
Regarding the cost-effectiveness of rainwater harvesting, high starting costs are a deterrent for its wider adaptation. Under saline irrigation, investing in a rainwater harvesting system rather than expanding the greenhouse cultivation area is more feasible since the increase in yield paid back is much faster. Some uncertainty remains regarding the feasibility of the system under subsequent dry hydrological years. Subsidizing the installation of rainwater harvesting systems can reduce these uncertainties and have a high added value for the local society and the level of provided ecosystem services.
Alexakis, D.D., Daliakopoulos, I.N., Panagea, I.S. and Tsanis, I.K., 2018. Assessing soil salinity using WorldView-2 multispectral images in Timpaki, Crete, Greece. Geocarto International, 33(4), pp.321-338. doi.org/10.1080/10106049.2016.1250826
I.N. Daliakopoulos, I.K. Tsanis, A. Koutroulis, N.N. Kourgialas, A.E. Varouchakis, G.P. Karatzas, C.J. Ritsema (2016) The threat of soil salinity: A European scale review. Science of the Total Environment http://dx.doi.org/10.1016/j.scitotenv.2016.08.177
Ioannis N. Daliakopoulos, Polixeni Pappa, Manolis G. Grillakis, Emmanouil A. Varouchakis, and Ioannis K. Tsanis (2016) Modelling soil salinity in greenhouse cultivations under a changing climate with SALTMED: Model modification and application in Timpaki, Crete. Soil Science 181(6), pp.241-251.
I. S. Panagea1, I. N. Daliakopoulos, I. K. Tsanis, and G. Schwilch (2015) Evaluation of soil salinity amelioration technologies in Timpaki, Crete: a participatory approach Solid Earth, 7, 177-190, DOI:10.5194/sed-7-2775-2015
The Timpaki basin is connected to the western Messara plain by the Geropotamos River through the Festos gorge, close to the ancient Minoan palace of Phaistos and encompasses an area of 50 km2 located in the central-south area of Crete with a mean elevation of 200m. The main geological coverage of the basin includes conglomerates, clays, silts, sands and marls that are deposited unevenly. Furthermore, the main land use in the Timpaki basin is olive groves, horticulture and greenhouses. The climate ranges between sub-humid Mediterranean and semi-arid with mild moist winters (average temperature: 12oC and dry hot summers (average temperature: 28oC) while the mean annual precipitation is estimated to be 500mm.
Main soil threat
Water supply in Greece is largely derived from groundwater sources. Intensive agriculture and high tourism activity are the two prime factors that strongly impact upon the available water resources of the island of Crete. The growth of agriculture in the Messara plain of Crete has had significantly impacted the water resources and ecosystem services of the area by substantially increasing water demand. This leads to the overexploitation of groundwater, which is a major resource for irrigation. This problem is exacerbated due to illegal water extraction, excessive irrigation, faulty pumping schemes and under prolonged dry climatic conditions, results in a negative water balance. This raises the major issue of concern being the seawater intrusion in coastal aquifers, such as the coastal Timpaki area. Simulation of seawater intrusion (left), 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.
Other soil threats
Irrigation affects ecosystem services of the area by substantially increasing water demand. This leads to the overexploitation of groundwater, which is a major resource for irrigation. This problem is exacerbated due to illegal water extraction, excessive irrigation, faulty pumping schemes and under prolonged dry climatic conditions, results in a negative water balance. This raises the major issue of concern being the seawater intrusion in coastal aquifers, such as the coastal Timpaki area. Simulation of seawater intrusion (left), 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.
Salinity is closely linked to other soil degradation issues. The decreased vegetation cover promotes vulnerability of soils to erosion and associated problems of reduced infiltration due to crusting and sealing of soil pores (Prager et al., 2011; Wong et al., 2010) as well as further loss of soil organic matter and nutrients. The subsequent loss of vegetation cover enhances the feedback of organic matter loss, erosion, and desertification. Messara Valley is also threatened by desertification due to poorly managed groundwater pumping for irrigation, which has caused a drop of the groundwater level by 20 m during the last decade.
Geology & Soils
In Crete, the large number of faults indicates an intense tectonic activity. The tectonic setting affected the integrity and continuity of the lithostratigraphic units and the faults bring in contact different lithostatigraphic units with different hydrogeological characteristics. Neogene deposits in Messara basin have undergone multidirectional extensional tectonic events with intervals of small, in duration and intensity degree of compression (Vafidis et al., 2013). The Timpaki sub-basin is separated from the rest Messara basin by Phaistos horst. It is filled with Neogene deposits, which are regarded as aquitard and it separates hydrogeologically the Timpaki basin from the eastern part of Messara basin. There is only an approximately 2km - wide passage through the horst, on which Geropotamos river flows towards the west. The Timpaki sedimentary basin was formed and evolved during Miocene. Pleistocene and Holocene deposits dominate in the Case Study (Panagopoulos et al., 2013). The Neogene formation crops out mainly to the north of the study area and underlies the Pleistocene deposits. Transmissivity values in the alluvium exceed 1×10-1 m2/sec while for the Lower Pleistocene the average value is about 1×10-2 m2/sec (Paritsis, 2005). The main geological coverage of the basin includes conglomerates, clays, silts, sands and marls that are deposited unevenly.
Soil groups and materials (WRB) (left) and Land Use in the Case Study (Source: JRC) (right)
There is no doubt that, with some exceptions, Crete was covered with forest before Neolithic times. Today, there is no natural forest left in the region (Bottema, 1980) but the natural landscape is dominated by scrublands, the typical Mediterranean garigue (Stobbelaar et al., 2000). The Cretan landscape has been cultivated since thousands of years, leading to 30% of its flora being linked to agriculture (CASCADE, 2013). Two main agro-ecological zones occur in the region: the hilly zone surrounding the plain, and the plain. Each zone displays different agro-ecological characteristics (Kabourakis, 1996) but also interacts with the other to the degree that it affects environmental variables such as water and fodder availability, soil preservation, fire hazard, etc. Major land use driving forces have been the growing importance of tourism and the impact of the European Common Agricultural Policy (CAP) (Kassa et al., 2002) that have also contributed to the decision of transform local marshes to cultivated land in the 80s (Stobbelaar et al., 2000).
Timpaki is a highly exploited area concerning the greenhouse cultivations, because of the favourable climatic conditions year round. Olive trees (43%), arable crops (39%) and horticulture (16%) comprise the main crops types with greenhouses playing a major role for the latter, also compared to the mother Municipality. Hellenic Statistic Authority (HSA, 2008) has identified a total of about 2,500 ha of cultivated land in Timpaki, while other estimates (Paritsis, 2005; Vafidis et al., 2013) estimate 7,800 ha of which 4,000 are irrigated almost exclusively by groundwater extraction. The majority of the 1,694 greenhouses found in the Prefecture of Heraklion (Tsakiridi, 2010) are in Timpaki and cover 3,580 m2 (Spyridaki, 2008). Crops are usually harvested twice a year and include non-indigenous species, mainly tomato (Solanum lycopersicum), cucumber (Cucumis sativus), zucchini (Curcubita pepo), eggplant (Solanum melongena), pepper (Capsicum anuumm) and green beans (Phaseolus vulgaris) (Thanopoulos et al., 2008).
|Area||Olive trees||Arable crops1||Horticulture||Citrus||Vine trees||Total|
|Timpaki||1,100 (43%)||1,005 (39%)||401.5 (16%)||37 (1%)||3 (0%)||2,540.2|
|Phaistos||13,090 (79%)||1,805 (11%)||1,404.3 (8%)||187.5 (1%)||62.4 (0%)||16,549.2|
1Major arable crops include watermelons, melon and potatoes.
Messara Valley’s climate is classified as dry sub-humid according to UNCED (Paris Convention on Desertification, 1994) definitions and its hydrological year can be divided into a wet and dry season (Tsanis and Apostolaki, 2008). Crete has a typical Mediterranean island environment with about 53% of the annual precipitation occurring in the winter, 23% during autumn and 20% during spring while there is negligible rainfall during summer (Koutroulis et al., 2010). Figure below shows the mean monthly precipitation estimated for Timpaki using measurement from the local meteorological station and E-OBS data. For the available record, precipitation shows no significant trend and remains stable at an annual rate of 504 mm. The climate ranges between sub-humid Mediterranean and semi-arid with mild moist winters (average temperature: 12oC) and dry hot summers (average temperature: 23oC) while the mean annual precipitation is estimated to be 500 mm. The average winter temperature is 12oC (with a record minimum of -0.2oC) while in the summer it is estimated at 23oC (with a record maximum of 44oC).
Average annual (left) and mean monthly (right) precipitation and temperature
at Timpaki derived from the E-OBS dataset and corrected for bias
Due to the geological situation the hydrogeology of the Timpaki basin is strongly connected to the Messara plain, although the almost impermeable Phaistos horst restricts water flow to the gorge of the Geropotamos. Groundwater pumping levels range between 3 and 7 m a.s.l. At the central part of the plain, between Timpaki and the Klematianos stream, well yields 100 m3/h with specific capacities of 20 to 40 m3/h/m drawdown are observed (Paritsis, 2005). The climate conditions (Figure 4.4) illustrate the strong seasonal differences between the hot and dry summer months and the wet winter. On average, 65% of the precipitation is lost due to evapotranspiration, 25% infiltrates towards ground water recharge and 10% is lost as runoff to the sea (Paritsis, 2005). Since evaporation increases with temperature, the recharge due to precipitation is negligible during the summer, coinciding with peak pumping rates.
Drivers and pressures
In Crete, as in the rest of the country, high profitability of irrigated farming has led to over-exploitation of water resources. The amount of water allocated for irrigation is estimated to be 82% of the total consumption. In general, water consumption has increased by more than 4% per year (LEDDRA Project, 2013). Most of the total water consumption is used in agriculture for the irrigation of olive groves, vineyards and vegetables and the CAP has significantly affected cropland areas and land use types. In Crete, many marginal areas under natural vegetation were cleared and monocultures have been installed. These areas become particularly vulnerable to erosion due to inadequate soil protection and reduction of infiltration rates which follows loss of organic matter content and soil structure decline.
The main source of irrigation water in Messara is groundwater as there is little surface water flow outside the winter months (Vardavas et al., 1997). Groundwater is the key resource controlling the economic development of the region, and it comprises a component of the environment under siege as water demand is increasing with time. The increased demand of water, either for domestic or agricultural use, cannot always be met, despite adequate average precipitation amounts. Water imbalance is often experienced, due to temporal and spatial variations of precipitation, increased water demand during summer months and the difficulty of transporting water due to the mountainous areas. The average annual water demand of the area was estimated at 60.9 Mm3 in year 2004, which was allocated 96.6% for agriculture, 3.2% for domestic use, and 0.2% for industrial supply. The agricultural demand was estimated from the irrigated area with coefficients depending on the type of crops, the optimum irrigation dose as suggested by pertinent studies, and the applied irrigation system (i.e. 25 m3/ha for olive trees, 35 m3/ha for grapes, 65 m3/ha for greenhouses) (RoC, 2006). The sequential occurrence of dry years in the 1990s has led to more intensive pumping to meet the irrigation demands. As a result, in 2000 the groundwater level was 45 m below the surface. Furthermore, during the last three years, the runoff of the Geropotamos River is close to zero. Lately, there have been growing concerns over the possible depletion or deterioration of the groundwater quality in the basin due to intensive pumping beyond the safe yield of the basin (Tsanis and Apostolaki, 2008).
Rural migration has also had a significant impact on cropland and land management practices. Large scale migration from rural to urban areas took place in Greece after the 1950s and since then rural population has continued to decrease (Daliakopoulos and Tsanis, 2014). As a result, land was either abandoned or rented. These conditions facilitated the over-exploitation of rural land from the few remaining farmers who often adopted harsh methods, such as uncontrolled burning of shrubs, otherwise condemned by neighboring users (Kosmas et al., 2000). At the same time, the total population of Crete has increased in the last four decades. The rate of increase was especially high in the area of Heraklion, putting significant pressure on land for transformation from agriculture to residential or industrial uses. Apart from urbanization, mass tourism has also put a pressure on the Cretan landscape in the last few decades. The total number of tourists in Crete is currently estimated at 1.7 million/year and under a business as usual global population and climate projection this number is expected to rise to 2.7 million/year until the mid of the century (Grillakis et al., 2015a, 2015b). As a result and a means to improve their financial profile, in less productive areas, particularly along the coast, farmers have sold their land to developers for the construction of tourist infrastructure.
By joining the European Economic Community in 1981, Greek agriculture became subject to the Common Agricultural Policy (CAP). Up until 1992, the aim of the CAP was to increase production, and to provide cheap rural products accompanied by reasonable rural incomes. Accordingly, agricultural production was intensified and mechanized, unique endogenous varieties were replaced by hybrids aimed for the needs of globalized markets, and the adoption of monocultures led to some extent to the loss of self-sufficiency. In addition, regional development, infrastructure, spatial planning policies and the implementation of Integrated Mediterranean Programmes constitute the factors that have considerably affected the exploitation of natural resources (Daliakopoulos and Tsanis, 2014). Greek farmers have re-orientated crop production towards the globalised market and Greek agriculture is no longer based solely on the needs of the country or the European Union. As a result, the country has simultaneously lost its self-sufficiency in products such as cereals, fruits, and vegetables (Kosmas et al., 2013). On the other hand, Greek exports have yet to adapt to traders demands such as weekly price stabilization and reliable, short lead times (time from order to delivery) as well as international consumer needs for direct delivery of certified quality fresh produce, thus deterring interest for long-term partnerships that will secure increased export quantities, a bigger market share and a strong brand presence (Valogiannis, 2012).
Status of soil threat
The CLEARWATER Project (Vafidis et al., 2013) uses electrical / electromagnetic geophysical methods to map water salinisation in Timpaki. They have observed that water salinisation occurs at depths of 30m. The biggest problem appears north of the stream Klematianos. During the MEDIS project (Paritsis, 2005), simulations and modelling of the area using the SEAWAT model under the assumption of variable density showed that the base of the saltwater front at the southern end is 550-600 m from the coastline. Similarly, in the northern part of the base of the front is located 1,500 m from the shoreline. This water is often used for irrigation with detrimental effects for production and the soil. Figure below shows Electric Conductivity (EC) and groundwater level measurements (RoC, 2009) that reveal conductivities close or over 1 dS/cm that are considered “High” according to Richards' (1954) classification system and can potentially hinder agricultural production. Recent water sampling has located irrigation water of over 2.25 dS/m which is considered “Unsuitable for agricultural use”. Recent soil sampling has revealed soil salinity of over 50 dS/m in several greenhouses, rendering their soil “Very strongly saline” according to Richards' (1954) classification system.
Measurement of electric conductivity EC at selected wells of Timpaki (Source: RoC, 2009)
Effects of soil threat on soil functions
The following table summarises and ranks the effects of soil salinity on the soil functions of Timpaki.
|Functions of soil||Explanation||Effect|
|Biomass production||Agricultural production is reduced or completely lost depending on the extent of soil salinisation.||H|
|Environmental interactions||Groundwater quality in the coastal zone is degraded possibly permanently.||M|
|Gene reservoir/ Biodiversity pool||Soil biodiversity in the coastal zone is reduced or completely lost.||H|
|Physical medium/ Source of raw materials||Raw materials and building capacity are not affected by salinisation.||N|
|Carbon pool||Effects are not known||U|
|Cultural heritage||Agriculture is an inseparable component of the Cretan tradition and any loss would greatly affect the landscape and the people. Nevertheless, the effect of soil salinisation can only be detected in the coastal zone other activities can also flourish.||L|
Maps on the current state of land use, soil degradation and soil conservation in the case study area have been produced using the WOCAT (World Overview of Conservation Approaches and Technologies) methodology
The steps of this process are as follows:
1) The area to be mapped is divided into distinctive land use systems (LUS).
2) The team gathers the necessary data on soil degradation and conservation for each LUS using a standardised questionnaire, in close consultation with local land users, and supported where possible by remote sensing or field data.
3) For each LUS, the soil degradation type, extent, degree, impact on ecosystem services, direct and indirect causes of degradation, as well as all soil conservation practices, are determined.
4) Once collected, the data is entered in the on-line WOCAT-QM Mapping Database from which various maps can be generated.
Following the principles of all WOCAT questionnaires, the collected data are largely qualitative, based on expert opinion and consultation of land users. This allows a rapid and broad spatial assessment of soil degradation and conservation/SLM, including information on the causes and impacts of degradation and soil conservation on ecosystem services.
More details about the methodology used to produce these maps and their interpretation can be found here.
Land Use (click on maps to expand)
The degree of degradation reflects the intensity of the degradation process, whilst the rate of degradation indicates the trend of degradation over a recent period of time (approximately 10 years).
The "effectiveness" of conservation is defined in terms of how much it reduces the degree of degradation, or how well it is preventing degradation. The Effectiveness trend indicates whether over time a technology has increased in effectiveness.
RECARE data repository
Data collected from the case study area for the project are held in a repository on the European Soil Data Centre (ESDAC) website hosted by Joint Research Centre (JRC). Below is a list of the data held.
To access the data click HERE (currently only accessbile with EUECAS login details)
Administrative and socio-economic setting
In administrative t,erms the Timpaki (or Tympaki) Municipal Unit (NUTS 5) has been merged in the municipality Faistos (NUTS 4) of the Heraklion regional unit (NUTS 3). The Region of Crete (NUTS 2), which includes Heraklion, is one of the 13 Regions of Greece and part of the GR4 First-level NUTS of the European Union (Aegean Islands, Crete or Nisia Aigaiou, Kriti). The Water Resources Department of the Prefecture of Crete (WRDPC) is the main managing authority in-charge of the water resources within the Messara basin and throughout Crete. Also, the Local Organizations of Land Reclamation (LOLR) has certain administrative authority in agreement with the decisions of the WRDPC. The EU WFD is a management directive that defines specific objectives, which have to be achieved by river basin management planners, mainly the WRDPC. The wells in the area are also controlled by the LOLR which regulates water use, e.g. pumping and irrigation rates and monitors water resources. The organization has extensive rights to establish rules and thresholds and as members, the farmers are entitled to vote and involve themselves in the LOLR’s decisions (Pipatpan and Blindow, 2005).
Contrary to many rural areas in Greece that face the effects of urbanization, the population of Timpaki has been steadily rising since the 50s. The main reason can be traced in the opportunities offered by the tourism sector in this coastal area (Figure 1.6a). On the other hand, contrary to the GDP of the Eurozone that largely rebounded after 2009, Greece has faced a prolonged crisis leading to little overall investments and financial contraction (Figure 1.6b).
Despite the measures that have been imposed by Local Authorities for the protection of water resources since 1984, their implementation has faced difficulties mainly due to private wells (92% in total) (Kritsotakis and Tsanis, 2009). If the estimated reduction of pumping rates is are not achieved despite imposed measures, the water table will continue to decline and consequently, the yield of wells will be gradually reduce from the margins of aquifer towards the centre. In the case of a dry year’s sequence, the deficiency of water in the region has been estimated at the order of 50%. If this deficiency is not covered by alternative freshwater resources or reduction of the consumption it is almost certain that more seawater will be abstracted leading to acute water and soil salinity problems.
Reduced soil salinity in Timpaki may be achieved applying mainly three measures, with different degrees of feasiblitiy, as follows: (1) best management practices in agricultural practices, (2) construction of decentralised water harvesting systems, and (3) the water resources management infrastructure at Prefecture level. Every applied measure to alleviate the water stress should set as a target the reduction of abstractions volume, in order to achieve good quantitative status (Kritsotakis and Tsanis, 2009). It should be noted that, in the near future, the Moires basin will be supplied with about 3 Mm3 from the Faneromeni dam, provided that additional groundwater resources are not abstracted thought pumping.
Relevant end-users and local stakeholder groups include;
The Region of Crete Directorates of Agriculture Development, Environmental and Spatial Planning, Water Resources Management and Civil Protection
Local municipal departments
Stakeholders in the area are working together to develop various water resource management scenarios in order to: (a) secure a sustainable future for agriculture and tourism; and (b) mitigate the soil threat such as salinization. Scenarios that are currently being processed within the context of salinization mitigation include pumping limitation of the existing wells and the prohibition of further pumping stations drilling. Groundwater recharge is another management option to help improve groundwater quality and avoid soil salinization. Under these conditions, with projections of further groundwater level decreases and the augmented irrigation needs, exploitation of nearby surface dams and the reuse of wastewater represent a priority for water resource management within the Timbaki basin.
Gender and stakeholder workshop
In a significant number of small and medium-size agricultural enterprises in Timpaki, Crete, Greece, women are actively involved in collecting, packaging and the standardization of agricultural products. These tasks require increased organizing capacity, dexterity and perseverance. Male farmers are mostly committed to heavier manual agricultural labor, which requires greater physical strength and endurance. In recent years, motivated by the modern way of life, financial hardships and government incentives, a few women farmers are also actively involved in management and leadership tasks of agricultural enterprises. In the first stakeholder workshop, held in Timpaki, the agricultural sector was mostly represented by male stakeholders, whereas the local government sector, NGOs, the research sector and the local press did include female representatives as well. Values from local soil related ecosystem services (ESS) mentioned by women in the stakeholder workshop were health and conservation for the next generations. Concerning a “Sustainable land management approach against soil salinisation”, women stakeholders were enthusiastic about the potential of adopting production methods that would respect the local environment and promote nature conservation thus offering direct and indirect benefits for them as well as the next generations. Women seemed more aware of a circular economy including a better lifestyle for the producer and a healthier product for the consumer while respecting the environment. The men in the workshop mostly valued those approaches that promised to promote sustainability while preserving overall efficiency and profits. Thus male stakeholders seem to focus more on the realistic aspects of day-to-day challenges.
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