Optimal irrigation planning for addressing current or future water scarcity in Mediterranean tree crops.

Water scarcity in the Mediterranean region is becoming a growing concern, threatening the viability of agriculture, which is one of the main economic sectors in many areas. The design of an optimal irrigation management plan, based on state-of-the-art measuring and modeling tools, can effectively contribute towards water saving efforts and potentially address the water scarcity issue in the region. This paper describes the development and application of an integrated decision-making system for the management of water resources of olive and citrus crops in the North of Chania, Crete, Greece. The system integrates different field measurements, for example 2088 soil moisture measurements taken within the study area, and modeling approaches to simulate flow in the unsaturated zone. After the successful calibration and validation of the model, the spatio-temporal representation of soil moisture and pore water pressure were used as guidance for developing optimal irrigation plans, taking into account the water needs of olive and citrus crops, aiming to maximize crop yield, agricultural income, and promote water saving efforts. According to the results, water use can be reduced by up to 36% during the dry season, compared to conventional irrigation practices for citrus trees. Similarly, for olive trees, the reduction in water use can reach up to 41%. The proposed methodology can also be cost-effective in terms of water value, saving about 40% from the typical water cost for irrigation in the study area. The impact of climate change on water resources availability in the area and water conservation efforts were also investigated for the period of (2019-2030). Results show that, comparing the Baseline, RCP 8.5 and RCP 4.5 climatic scenarios, the highest savings on average are observed for emission scenario RCP 4.5 with 53.3% water savings for olive trees and 46.7% for citrus trees.

An integrated method for assessing drought prone areas - Water efficiency practices for a climate resilient Mediterranean agriculture.

This paper presents a new integrated GIS modeling method to assess drought vulnerability using multi-criteria analysis. The proposed methodology is an improvement over previous methods since it incorporates both dynamic and static factors that may affect water dynamics and contribute to water scarcity. These factors are: a) precipitation, b) evapotranspiration, c) soil water content, d) soil depth, e) artificial drainage, f) depth to water table, g) runoff accumulation, and h) saltwater intrusion zones. The above factors and their corresponding maps were fuzzified and spatially overlayed in order to obtain the final drought vulnerability map. The map depicts the spatial distribution of drought vulnerability represented by five classes ranging from very low to very high vulnerability. The proposed methodology was applied to the Greek island of Crete located in the Southeast Mediterranean region. The island of Crete is one of the most drought-prone areas in the region, while at the same time the island's economy relies strongly on agriculture and tourism. The derived results show that drought vulnerability is more severe in the eastern part of the island and that the coastal zones of the entire island are drought-prone areas. Also, according to the results, 19% of the island's area is characterized as "very highly vulnerable to drought". This percentage varies significantly across the prefectures, with Rethymnon having the lowest vulnerability (2.8%), followed by the prefectures of Chania (6.3%), and Heraklion (17.3%), while the prefecture of Lassithi is the most vulnerable to drought (51.4%). The developed methodology was validated using historical data for drought affected areas in Crete, which is not always addressed in publications. Moreover, in this study, sustainable agricultural practices that ensure water efficiency especially in drought prone areas are proposed. These practices can be adopted by farmers to promote climate resilient agriculture in the Mediterranean region.

Assessing the efficiency of a coastal Managed Aquifer Recharge (MAR) system in Cyprus.

Managed Aquifer Recharge (MAR) is becoming an attractive water management option, with more than 223 sites operating in European countries. The quality of the produced water, available for drinking or irrigation processes is strongly depended on the aquifer's hydrogeochemical characteristics and on the MAR system design and operation. The objective of this project is the assessment of the operation efficiency of a MAR system in Cyprus. The coupling of alternative methodologies is used such as water quality monitoring, micro-scale sediment sorption experiments, simulation of groundwater flow and phosphate and copper transport in the subsurface using the FEFLOW model and evaluation of the observed change in the chemical composition of water due to mixing using the geochemical model PHREEQC. The above methodology is tested in the Ezousa MAR project in Cyprus, where treated effluent from the Paphos Waste Water Treatment Plant, is recharged into the aquifer through five sets of artificial ponds along the riverbed. Additionally, groundwater is pumped for irrigation purposes from wells located nearby. A slight attenuation of nutrients is observed, whereas copper in groundwater is overcoming the EPA standards. The FEFLOW simulations reveal no effective mixing in some intermediate infiltration ponds, which is validated by the inverse modeling simulation of the PHREEQC model. Based on the results, better control of the infiltration capacity of some of the ponds and increased travel times are some suggestions that could improve the efficiency of the system.

Groundwater footprint methodology as policy tool for balancing water needs (agriculture & tourism) in water scarce islands - The case of Crete, Greece.

In many Mediterranean islands with limited surface water resources, the growth of agricultural and touristic sectors, which are the main water consumers, highly depends on the sustainable water resources management. This work highlights the crucial role of groundwater footprint (GF) as a tool for the sustainable management of water resources, especially in water scarce islands. The groundwater footprint represents the water budget between inflows and outflows in an aquifer system and is used as an index of the effect of groundwater use in natural resources and environmental flows. The case study presented in this paper is the island of Crete, which consists of 11 main aquifer systems. The data used for estimating the groundwater footprint in each system were groundwater recharges, abstractions through 412 wells, environmental flows (discharges) from 76 springs and 19 streams present in the area of study. The proposed methodology takes into consideration not only the water quantity but also the water quality of the aquifer systems and can be used as an integrated decision making tool for the sustainable management of groundwater resources. This methodology can be applied in any groundwater system. The results serve as a tool for assessing the potential of sustainable use and the optimal distribution of water needs under the current and future climatic conditions, considering both quantitative and qualitative factors. Adaptation measures and water policies that will effectively promote sustainable development are also proposed for the management of the aquifer systems that exhibit a large groundwater footprint.

Groundwater Modeling and Remediation Scenarios of a Hexavalent Chromium Plume Released from an Industrial Site.

In recent years, high concentrations of hexavalent chromium [Cr(VI)] have been found in the groundwater system of the Asopos River Basin. This work focuses on a Cr(VI) plume detected in the industrial area of Inofyta, the most important contamination hot spot of the Asopos River Basin. A groundwater flow and Cr(VI) transport model was developed to assess the behaviour of the plume and investigate the location of a suspected nearby source zone. According to the model results, the suspected source zone location is highly probable and the Cr(VI) plume does not migrate significantly. Based on the above findings, it is believed that the remediation effort could potentially be very effective in the area, if the remediation plan is designed properly. In order to assess the remediation potential of (a) natural attenuation and (b) polyphenol-coated nZVI treatment, two model scenarios were created and their results were compared and discussed.

Large scale groundwater flow and hexavalent chromium transport modeling under current and future climatic conditions: the case of Asopos River Basin.

In recent years, high concentrations of hexavalent chromium, Cr(VI), have been observed in the groundwater system of the Asopos River Basin, raising public concern regarding the quality of drinking and irrigation water. The work described herein focuses on the development of a groundwater flow and Cr(VI) transport model using hydrologic, geologic, and water quality data collected from various sources. An important dataset for this goal comprised an extensive time series of Cr(VI) concentrations at various locations that provided an indication of areas of high concentration and also served as model calibration locations. Two main sources of Cr(VI) contamination were considered in the area: anthropogenic contamination originating from Cr-rich industrial wastes buried or injected into the aquifer and geogenic contamination from the leaching process of ophiolitic rocks. The aquifer's response under climatic change scenario A2 was also investigated for the next two decades. Under this scenario, it is expected that rainfall, and thus infiltration, will decrease by 7.7 % during the winter and 15 % during the summer periods. The results for two sub-scenarios (linear and variable precipitation reduction) that were implemented based on A2 show that the impact on the study aquifer is moderate, resulting in a mean level decrease less than 1 m in both cases. The drier climatic conditions resulted in higher Cr(VI) concentrations, especially around the industrial areas.

Assessing groundwater quality in Greece based on spatial and temporal analysis.

The recent industrial growth together with the urban expansion and intensive agriculture in Greece has increased groundwater contamination in many regions of the country. In order to design successful remediation strategies and protect public health, it is very important to identify those areas that are most vulnerable to groundwater contamination. In this work, an extensive contamination database from monitoring wells that cover the entire Greek territory during the last decade (2000-2008) was used in order to study the temporal and spatial distribution of groundwater contamination for the most common and serious anionic and cationic trace element pollutants (heavy metals). Spatial and temporal patterns and trends in the occurrence of groundwater contamination were also identified highlighting the regions where the higher groundwater contamination rates have been detected across the country. As a next step, representative contaminated aquifers in Greece, which were identified by the above analysis, were selected in order to analyze the specific contamination problem in more detail. To this end, geostatistical techniques (various types of kriging, co-kriging, and indicator kriging) were employed in order to map the contaminant values and the probability of exceeding critical thresholds (set as the parametric values of the contaminant of interest in each case). The resulting groundwater contamination maps could be used as a useful tool for water policy makers and water managers in order to assist the decision-making process.

Statistical analysis and ANN modeling for predicting hydrological extremes under climate change scenarios: the example of a small Mediterranean agro-watershed.

The purpose of this study was to create a modeling management tool for the simulation of extreme flow events under current and future climatic conditions. This tool is a combination of different components and can be applied in complex hydrogeological river basins, where frequent flood and drought phenomena occur. The first component is the statistical analysis of the available hydro-meteorological data. Specifically, principal components analysis was performed in order to quantify the importance of the hydro-meteorological parameters that affect the generation of extreme events. The second component is a prediction-forecasting artificial neural network (ANN) model that simulates, accurately and efficiently, river flow on an hourly basis. This model is based on a methodology that attempts to resolve a very difficult problem related to the accurate estimation of extreme flows. For this purpose, the available measurements (5 years of hourly data) were divided in two subsets: one for the dry and one for the wet periods of the hydrological year. This way, two ANNs were created, trained, tested and validated for a complex Mediterranean river basin in Crete, Greece. As part of the second management component a statistical downscaling tool was used for the creation of meteorological data according to the higher and lower emission climate change scenarios A2 and B1. These data are used as input in the ANN for the forecasting of river flow for the next two decades. The final component is the application of a meteorological index on the measured and forecasted precipitation and flow data, in order to assess the severity and duration of extreme events.