Sediment Transport in the Koiliaris River of Crete

AbstractIn this paper, a study of the sediment transport in a complex Mediterranean watershed (i.e. the Koiliaris River Basin of Crete) consisting of temporary flow tributaries and karstic springs is presented. Both daily flow data (2005-2013) and monthly sediment concentration data (2011-2013) were used to calibrate the modified Soil and Water Assessment Tool (SWAT) model, designed to simulate the hydrology, sediment yield and water quality of ungauged watersheds, and augmented with a karst flow model in order to simulate the contribution of the extended karst to the spring discharge in the basin. The results showed good agreement between observed and model values for both flow and sediment concentration. However, since no data representative of high sediment concentration conditions were available, such as during extreme flow events, an automated sediment sampling device (Sediment Trap), which allows for flow weighted sampling, has been developed and is detailed in this paper. This device is undergoing testing to ensure it can provide accurate estimates of sediment yield, especially during a flush flood event when large amounts of sediment are carried downstream. The sediment measurements will then be used to calibrate and verify the sediment transport simulations of the Koiliaris River watershed generated by the SWAT model. The sediment transport simulations and the development of the automated sampling device were part of the preliminary work for the pilot application of the “Cybersensors” infrastructure in the Koiliaris River. The Cybersensors research project aims to develop an intelligent integrated monitoring system, which will utilize electrochemical and optical sensors, and will allow for high-frequency monitoring of the physical and chemical parameters of a river flow and thus the rapid detection of environmental change during episodic events, as well as for long term monitoring

Soil Water Characteristics of European SoilTrEC Critical Zone Observatories

Most of soil functions depend directly or indirectly on soil water retention and transmission, which explains their importance for many environmental processes within Earth's Critical Zones. Soil hydraulic properties are essential in irrigation and drainage studies for closing water balance equation, for predicting leaching of nutrients, for water supply to plants, and for other agronomical and environmental applications. Soil hydraulic properties reflect the structure of the soil porous system comprising pores of different geometry and sizes. This investigation comprises a detailed analytical study of soil hydraulic properties and climate conditions at 18 methodologically selected sites in Damma Glacier, Slavkov Forest, Marchfeld, and Koiliaris Critical Zone Observatories of SoilTrEC project. The local moisture regimes were assessed on a long-term basis by the Newhall model. The experimental data for soil water content at different potentials were used for assessing water storage capacity, pore size distribution, parameters of fitted retention curve equation, curve slope at the inflection point, and water permeability characteristics of each soil horizon. The differences of soil water retention and transmission characteristics-as fundamental properties describing soil structure-were explained by the different stages of soil profile development, parent materials, organic matter content, and land use histories

Modeling the impact of carbon amendments on soil ecosystem functions using the 1D-ICZ model

In the next four decades, humanity needs to double food and energy production and increase the supply of clean water by over 50% while mitigating and adapting to climate change. A central element in the strategy of addressing these major environmental challenges is to maintain the central role of Earth's essential soil functions and related ecosystem services. Many soil functions are affected by soil structure in terms of particle aggregation and porosity. The objective of this work is to model soil structure and biomass dynamics, nutrients uptake, and yields using the 1D Integrated Critical Zone (1D-ICZ) model which is a mechanistic mathematical description of soil processes and functions. The 1D-ICZ model simulates the coupled processes that underpin major soil functions including water flow and storage, biomass production, carbon and nutrient sequestration, pollutant transformation, and supporting biological processes, and thus is capable of quantifying essential soil ecosystem services. The model was validated using data derived from a field experiment where tomato plants were grown using different treatments of commercial mineral fertilizers, compost, manure, and a 30% manure–70% compost amendment. Detailed data have been collected over four growing seasons on soil and soil solution chemistry, aggregate formation, and plant production. The model has been able to capture the biomass production, the temporal dynamics of the water-stable aggregate formation and the dynamics of carbon and nutrient sequestration in the different sizes aggregates as well as the variability of water filtration and transformation efficiency in the different amendment treatments. The model results demonstrate the value of applying computational simulation tools such as the 1D-ICZ model to test options for improved land management measures and to support sustainable land care practices

Flood generation and classification of a semi-arid intermittent flow watershed: Evrotas river

Hourly water level measurements were used to investigate the flood characteristics of a semi-arid river in Greece, the Evrotas. Flood events are analysed with respect to flood magnitude and occurrence and the performance of Curve Number approach over a period of 2007-2011. A distributed model, Soil and Water Assessment Tool, is used to simulate the historic floods (1970-2010) from the available rainfall data, and the performance of the model assessed. A new flood classification method was suggested the Peaks-Duration Over Threshold method that defines three flood types: 'usual', 'ecological' and 'hazardous'. We classify the basin according to the flood type for the most serious past simulated flood events. The proportion of hazardous floods in the main stream is estimated to be 5-7% with a lower figure in tributaries. Flood Status Frequency Graphs and radar plots are used to show the seasonality of simulated floods. In the Evrotas, the seasonality pattern of hazardous flood is in agreement with other studies in Greece and differs from other major European floods. The classification in terms of flood types in combination with flood type seasonality is identified as an important tool in flood management and restoration. © 2013 International Association for Hydro-Environment Engineering and Research

Integrated critical zone model (1D-ICZ): a tool for dynamic simulation of soil functions and soil structure

Food security should be addressed in relation to soil sustainability and sustainable land care, and examined within the science framework of Earth's critical zone as an integrated system that includes Earth surface interactions, connected to soil functions, and ecosystem services. There is a great need to develop critical zone mathematical models that will simulate and quantify soil functions and that can be used as management tools to address soil sustainability and land care practices. The integrated critical zone model, 1D-ICZ, couples computational modules for soil organic matter dynamics, soil aggregation and structure dynamics, bioturbation, plant productivity and nutrient uptake, water flow, solute speciation and transport, and mineral weathering kinetics. The 1D-ICZ model, coupled with new pedotransfer functions to predict bulk soil properties, introduces for the first time a model that dynamically links soil structure characteristics and hydraulic soil properties by simulating their changes under varying meteorological conditions and plant growth. Field data from a Mediterranean olive grove at the Koiliaris Critical Zone Observatory (CZO) were used to simulate carbon addition to soil and agricultural management scenarios, in order to illustrate the model's ability to quantify soil management impact on soil functions and biogeochemical transformations and fluxes. The 1D-ICZ model can be used to assess, understand, and quantify the complex interactions between the different processes in the soil-plant-water system and can be applied as a tool to design sustainable agricultural management practices, taking into consideration synergy and trade-offs among soil functions

Linkages between aggregate formation, porosity and soil chemical properties

Linkages between soil structure and physical–chemical soil properties are still poorly understood due to the wide size-range at which aggregation occurs and the variety of aggregation factors involved. To improve understanding of these processes, we collected data on aggregate fractions, soil porosity, texture and chemical soil properties of 127 soil samples from three European Critical Zone Observatories. First, we assessed mechanistic linkages between porosity and aggregates. There was no correlation between the fractions of dry-sieved aggregates (N1 mm, DSA) and water-stable aggregates (N0.25 µm, WSA). Soil microporosity and micro + mesoporosity increased with increasing abundance of aggregates, though this correlation was only significant for the WSA fraction. The fraction of DSA did not affect the overall porosity of the soil, but affected the ratio between micro- and mesopores (¿30 kPa/¿0.25 kPa), suggesting that micropores are dominantly located within DSA whereas mesopores are located in betweenDSA and loose particles. Second,we studied the relations between the physical and chemical soil properties and soil structure. Soil texture had only a minor effect on the fractions ofWSA and DSAwhereas Fe-(hydr)oxide content was correlated positively with bothWSA fraction and porosity. This may be attributed to Fe-(hydr)oxides providing adsorption sites for organic substances on larger minerals, thereby enabling poorly reactive mineral particles to be taken up in the network of organic substances. The fraction ofWSA increased with an increase in the soil organic carbon (SOC) and Fe-(hydr)oxides content and with a decrease in pH. This pH-effect can be explained by the enhanced coagulation of organically-coated particles at a lower pH. Overall, this study indicates that mechanistic linkages exist between soil chemical properties, aggregate formation and soil porosity

Sediment provenance, soil development, and carbon content in fluvial and manmade terraces at Koiliaris River Critical Zone Observatory

The purpose of this study was the investigation of sediment provenance and soil formation processes within a Mediterranean watershed (Koiliaris CZO in Greece) with particular emphasis on natural and manmade terraces. Material and methods Five sites (K1–K5) were excavated and analyzed for their pedology (profile description), geochemistry [including rare earth elements (REEs) and other trace elements], texture, and mineralogy along with chronological analysis (optical luminescence dating). The selected sites have the common characteristic of being flat terraces while the sites differed with regard to bedrock lithology, elevation, and land use. Results and discussion Three characteristic processes of soil genesis were identified: (1) sediments transportation from outcrops of metamorphic rocks and sedimentation at the fluvial sites (K1–K2), (2) in situ soil development in manmade terraces (K3, K4), and (3) strong eolian input and/or material transported by gravity from upslope at the mountainous site (K5). REE patterns verified the soil genesis processes while they revealed also soil development processes such as (a) calcite deposition (K1), (b) clay illuviation and strong weathering (K4), and (c) possibly fast oxidation/precipitation processes (K3). Carbon sequestration throughout the soil profile was high at manmade terraces at higher elevation compared to fluvial environments due to both climatic effects and possibly intensive anthropogenic impact. Conclusions Soils at Koiliaris CZO were rather young soils with limited evolution. The different soil age, land use, and climatic effect induced various soil genesis and soil development processes. The manmade terraces at higher elevation have much higher carbon sequestration compared to the anthropogenic impacted fluvial areas

The mirage toolbox : An integrated assessment tool for temporary streams

The assessment of the ecological status of water bodies, as requires by the European Water Framework Directive, can raise a number of problems when applied to temporary streams. These problems are because of the particular physical, chemical and biological conditions resulting from the recurrent cessation of flow or even the complete drying of the stream beds. In such non-permanent water bodies, the reference quality standards developed for permanent streams may only be applicable under certain circumstances or may not be applicable at all. Work conducted within the collaborative EU-funded project Mediterranean Intermittent River ManAGEment (MIRAGE) has addressed most of these difficulties and has used diverse approaches to solve them. These approaches have been brought together in the so-called MIRAGE Toolbox. This toolbox consists of a series of methodologies that are designed to be used in a sequential manner to allow the establishment of the ecological and chemical status of temporary streams and to relate these findings to the hydrological status of the streams. The toolbox is intended to serve the following purposes: (i) the determination of the hydrological regime of the stream; (ii) the design of adequate schedules for biological and chemical sampling according to the aquatic state of the stream; (iii) the fulfillment of criteria for designing reference condition stations; (iv) the analysis of hydrological modifications of the stream regime (with the definition of the hydrological status); and (v) the development of new methods to measure the ecological status (including structural and functional methods) and chemical status when the stream's hydrological conditions are far from those in permanent streams.</p