Reservoirs Positioning Through GIS: a Key for a Local Development and Exploitation Of

Reservoirs positioning through GIS: A key for a local development and exploitation of surface runoff

E. Pissias1, A. Psarogiannis1, K. Kalogeropoulos2

1Department of Surveying Engineering, Technological Educational Institute of Athens, email: , Ag. Spyridonos Str., 12210 Aigaleo, Athens, Greece

2Department of Geography, Harokopio University, email: , El. Venizelou Str., Kalithea, 17671, Athens, Greece, tel. 00302109549347

Abstract During the last decades, a key factor that policy makers take into consideration in the assessment of the environment is climate change. This global physical process is already causing problems in natural and human environment. In the future these problems expected to be maximized. Therefore, the pressure that will be exerted on water resources is expected to be even higher as a result increasingly in water shortages in most areas. The management of water resources requires, depending on the needs of each region and each season, adopting management techniques to meet these needs. The reduction of ground water resources, degradation of their quality and intensive utilization signifies the necessity of promoting projects of exploitation of surface runoff. Projects that ensure the utilization of surface water (dams, reservoirs, dams, refineries) are more environmentally friendly and contribute to the protection of the environment, to energy savings and in some cases to the production of energy from renewable energy sources. These projects are made even more attractive because of holding unused quantities of water, greater consumer protection, the possibility of multiple uses of water and the creation of new jobs. This paper presents a methodology of choosing the suitable places in order to construct small reservoirs for the utilization of surface runoff. The use of primary data such as meteorological and spatial data in a Geographic Information Systems (GIS) context, with the integration of suitable hydrological model can reveal positions/places that are appropriate for constructing small reservoirs. Andros Island (Cyclades, Greece) is the study area for this current proposed methodology. Several places on the island were examined, and ultimately, three were chosen in order to create small reservoirs.

Keywords: Reservoirs, adequate technology, local development, modeling, GIS.

1. Introduction

During last decades, the pressure which arises on water resources has increased significantly due, mainly, to population growth, immigration to urban and coastal areas, climate change, and desertification. In the future this pressure is expected to be maximized. Therefore, the problems will be even higher as a result of water shortages in most areas.

The biggest challenge in dryland urban and rural economic activities is low and erratic rainfall. Another challenge, which constitutes the specificity of water resources management (WRM) plans in insular clusters, is that of territorial-geographical discontinuity.

In order to solve those exceptional WRM problems and meet these needs, the adoption of adequate socio-economic approaches, on top of them those assuring demand reduction, is required. It requires also deep and particular geographic analysis of spatial factors and constraints, as well as suitable technologies preventing from the implementation of heavy –although vulnerable- and non-coherent -although expensive - water systems. The depletion of ground water resources, related to the degradation of their quality due to intensive exploitation of aquifers as well as of fossil waters, shall also prevented. The use of non-renewable resources has to be minimized if not forbidden and the promotion of projects aiming at an optimal valuation of surface runoff has to be encouraged.

Projects that ensure the utilization of surface water through adequate, decentralized, small scale harvesting systems (small dams, mountainous-hilly reservoirs) could be more environmentally friendly than big scale ones or those over-exploiting ground water. Those projects may also serve to several parallel tasks, among them the protection of forester environment, and, in some cases, the implementation of local scale hydro-power energy systems. Those surface water management projects could become even more attractive if related with appropriate technologies aiming at the use of locally-regionally existing human and natural resources and produced materials. In that case they strengthen local-regional development processes and increase the opportunity for creation of new jobs. Taking into consideration the developmental constraints which arisen during the actual economic crisis, the above low capital investment and running cost water management schemes become “projects of the moment” challenging for local development.

This paper presents also a new technology package that can help build effective, low-cost systems for harvesting rainwater. This will deliver larger and more stable water supplies for peak season’ s urban uses, for crops and livestock, even in very dry and isolated areas (Drouart, 1999). It is based on a methodology of choosing (selecting) the water basins and the suitable sites within, for the construction of small reservoirs. The production and use of primary data such as meteorological and spatial data inserted in a Geographic Information Systems (GIS) context, using a suitable hydrological model can reveal sites that are appropriate for the construction of those reservoirs. Andros Island (Cyclades, Greece) is the study area for the proposed methodology[1]. Several water basins and sites on the island were identified, among them seven (7) have been identified according to our principal criteria and, ultimately, three (3) were studied in order to create small reservoirs.

2. The historical background & the future of reservoirs in Greece

2.1 Complementarity, integrality and adversariality within WRM schemes.

The concepts of complementarity as well as the concept of adversariality between different WRM schemes are reflecting advantageous but also inappropriate solutions. Analysis of recent technical practices in Greek insular clusters has proven that combination of different type of water infrastructures could be succesfull since assuring a variety of alternative supply capacities. Nevertheless, practices that have been -or still are- implemented, considered either as the sole valuable practice, for example water drillings, or as the main practice which has to be combined with other complementary practices, shall be, at now days, reconsidered. The question then which arises is to evaluate the 3 main-stream practices, referring to the 3 following technologies: a) water drillings, b) dams and reservoirs, c) sea water desalination units, within a different WRM context.

The design of an integrated WRM system in an inland region is subject to the territorial discontinuity. From this fact resulting two management models, the first is an open-trans territorial and the second is a local model. The first model, which is a typical model of WRM, is concerning mainly the so-called arid islands[2] and relies on sea water transport from other areas that have a potential surplus. This model includes sometimes the extremely high cost solution of water transport by ship[3] and sometimes the solution of expensive water transfer projects with underwater pipelines (see Aegina). The second model is almost entirely local and seeks the water self-sufficiency by exploiting local natural hydrosystem of each island and possibly the installation of a desalination plant.

Water resources management was more empirical in the past, in a collective or individual level, and was based on well-known solutions from rural-residential island tradition like house cisterns (small open tanks) for drinking water or shallow irrigation wells. Today, these solutions are maintaining their usefulness. These solutions also have positive environmental sign, as they are of low cost and probably the only problem lies to their low efficiency which makes them inadequate in modern times. The solution of drillings of reasonable depth has been for some time a satisfactory solution and has potential to provide irrigation water also in reasonable quantities. This period, which in some islands ended during 70's and in other during 80's, the water balance was equilibrated without any threat for the aquifers.

With the increasing needs of the new high consumption tourist-rural development model of that period, the drillings proliferate at high rates while over pumping of groundwater is observed from greater depths. The rise of this phenomenon is largely due to uncontrolled and, in most cases, to its expansion resulting in depletion of the normal underground aquifer and the rapid degradation of water quality. It was then the period when has been attempted unsuccessfully the implementation of a regulatory framework for water wells and when also a first dams and reservoirs program has been applied. It was then a period when the first desalination plant in Syros has been inaugurated, followed later (around 2000), by the provision, design and installation of other units in most of the islands in order to partially cover the water supply needs exclusively.

This process is well known and the descriptive of each sector (or by case) as well as the physical inventory yield of main hydrosystems have, to some extent, taken place. But the critical assessment of public interest, at least, technical projects which make up the water management infrastructure, through a system of continuous monitoring and evaluation, didn’t took place.

However, explicitly or implicitly, the technical system of production, design and implementation of projects in the country, which includes research groups, consultants, manufacturers-suppliers, public services, local government and individuals that influence decision making processes, especially the "subsystem" that operates in islands, dictates the shape and trends in terms of the basic categories of projects mentioned above. The first category, which relates to household infrastructure (mainly cisterns), was not enough supported as it should, the second, which is concerning groundwater continues its excessive anti-environmental activity. The third one is relating to desalination and is now gaining ground, the fourth, known as small dams, is falling, despite its powerful advantages, one of which is energy autonomy in times of intense questioning of headlong energy-environmental crisis. Other methods, some of these environmentally friendly (reusing grey waters and / or waste water), are not yet supported.

This paper certainly cannot cover in any way the above failures; however, it can evaluate, to some extent, the findings of other research projects and studies[4] mentioned in the area of Aegean. It can also draw conclusions from the research work which have been done in Andros Island and concerns to the local water system and the existent, or rather non-existent projects of technical-hydraulic infrastructures.

The summary of these findings highlights two principles where the first puts and encourages complementarity of different types of projects and the second one limit and / or exclude certain types of projects focusing on contrariety in terms of scale but also in their physical and anthropogenic/geographic factors that constitute each water system. The first principle serves the criterion of diversity and complementarity and interchangeability of the solutions which ensures the reduction of risk arising from a unidimensional development of a management plan. The second principle obeys to the criterion of exclusion of inappropriate and abusive solutions which tend both to the depletion of water resources and to destruction of the hydrosystem (Point, 1999).

2.2 The challenge of small reservoirs.

It is known that reservoirs of capacity of billions m3 have built and probably, unfortunately, the same is going to be in the future (and of course reservoirs of hundreds or tens of millions m3 of capacity). These reservoirs, despite their huge differences between them, are classified in the category of large reservoirs-dams. The lower category, that of reservoirs of few dozen or even of few million m3 (in single digits) is considered a medium category, while an even lower category, comprizing less than 2-3 million m3 capacity dams and reservoirs is characterized as a class of small reservoirs. According to the research program HYDROMED for small mountainous and upland reservoirs in North and Southeast Mediterranean characterizes as small reservoirs those classified between a few tens of thousands up to 1,000,000 m3.

Neverthelees, it' s less known, almost not known in our country, that more than 90% of reservoirs, actually under construction worldwide, are small reservoirs, that some countries have the privilege to be covered by extended and dense small reservoir “chains”, among them many Mediterranean countries north and south. Greece is an exception, maybe the biggest exception.

In this current research project, small mountainous reservoirs are characterized those which are serving purposes of local development (Helvetas, 1985) are absolutely safe[5] (Z according ICOLD classification < 20) and which the relevant international experience is classifying in a range of capacity from 40,000 to 100,000 m3. Without of course excluding recommendations of the project for small deviations.

The purpose of this paper is to support the idea of the creation of a network of small, really small reservoirs, of an adequate technology, engineering, technique and know how, using local human resources and materials, therefore, they are projects of low cost and of high domestic-local added value [USG, 1965; USDI, 1987). The methodological choice (in order to support this objective) is primarily the comparative juxtaposition of specific concepts and related works belonging to the same technological 'family', as in this case the family of reservoirs, and only secondarily the critical approach to issues and arguments concerning general WRM frames, reffering to:

§ The superiority of the integrated design versus the piecemeal planning in WRM, e.g. multidimensional versus unidimentional approach, complementarity versus exclusivity, etc.

§ The comparative evaluation of the general usefulness of a particular method of utilization of water resources in relation to another method, such as, the use of runoff versus the groundwater exploitation and vice versa.

§ The juxtaposition of a technical solution over other technical solutions, such as dams against drilling or desalination plants and vice versa.

The chosen methodology does not focus to the rivalry of a technical choice to another, of a different kind, option, but between similar technical choices, of radically different scale projects, such as, for example, the rivalry between reservoirs of suitable small scale over others, allegedly as small (however, for our particular insular reality), rather medium and bigger, absolutely of improper scale. This methodology deals with the philosophy of the small reservoir, the prioritizing of goals, objectives and priorities, the socioeconomic and environmental considerations, the application of a specific technology and technique, etc.

The result of our research is the result of a thorough multicriteria analysis, where the criteria have been pre-processed to get rid of established rationalities such as: