Hydrogeology and its relation to other disciplines

Transcription

1 PART 1 Introduction Hydrogeology and its relation to other disciplines Hydrogeology is the science of water inside the earth. The name was introduced by J.-B. Lamarck (picture) in From Greek: υδραινω = hydros = water γεο = geo = earth λογος = logos = science Table 1. Relation of hydrogeology to other disciplines. Geomorphology Stratigraphy Tectonics Topography Soil science Mineralogy and petrology Chemistry Biology Climatology Physics Fluid mechanics Mathematics Statistics macroscopic geological properties of materials through which ground water flows physical, chemical and biological properties of the environment and processes outside forcing fluid flow fluid and media properties

2 Introduction 2 History of hydrogeological concepts Table 2. Development of hydrogeological ideas y ago pumping wells China medical use of mineral water 1700 BC Joseph s well, near Cairo, nearly 100 m deep Egypt ~700 BC quanat (qanat, kanat) - tunnels delivering water Urartu civilization (see description below table) 5 th century BC Thales of Miletus: Greece - land floats on water - sea water is driven by the wind into the interior of the earth, where it 500 BC Greece/Egypt 4 th century BC Greece 1 st century BC Rome rises to the surface due to pressure of rocks Anaxagoras of Clazomenae: - water in the sea was produced on land and flowed as rivers to the sea. Rivers depend on rain and on waters within the earth. And the Nile rises in summer due to the water that comes from snowmelt in Ethiopia. Aristotle: - sea water evaporates and falls on land, where it condensates - cooling air in rock spaces (caves) produces ground water - rocks are sources of minerals in water ("water is essentially of the same quality as the ground through which it flows") Marcus Vitruvius Pollio: - rain and melting snow penetrate rocks (-> infiltration) - presence of water depends on the soil type (see Table 3 below) - circulation of water in nature 2000 yr BP Philip of Trachonitis: - threw chaff into a crater lake and reported that the chaff had appeared downgradient in a spring Note: Mazur (1976) showed that this experiment could not have been a success. ca AD Persia Karadi: - circulation - pressure - field experiments - water quality

3 Introduction 3 Table 2. Development of hydrogeological ideas Perrault: - data from rain gauges - first estimation of discharge of the Seine River: multiplied precipitation by drainage area and found that the volume was six times of the discharge of the Seine > first quantitative hydrology Mariotte: - similar observation - infiltration, water-bearing and impermeable horizons, rainfall and recharge -> father of hydrology 1693 Edmund Halley: - evaporation experiment which showed that sufficient amount of water is evaporated from the oceans 1802 Lamarck: Austria Modern - introduced the term "hydrogeology" Darcy: - flow through porous media Dupuit: - flow to a borehole Forchheimer: - mathematics of flow in porous media Suess: - juvenile water comes from magma (concept) Gofer: - fossil water is formed in the crust in previous geological periods since the 1950s

4 Introduction 4 Examples - Qanats (Biswas, 1970, History of hydrology) About 700 BC, Urartu civilization (modern Armenia and eastern Turkey) developed qanats (quanats, kanats). A qanat is an underground channel that carries water over long distances. Advantages of qanats: they cut evaporation, provided transport, kept water cool and uncontaminated. Started in Armenia, spread to Persia, Egypt and India. The Urartu qanat was designed by engineer Muganni, who first located water-bearing strata by drilling many test wells, then mother wells in the specified places with a tunnel between them. In Egypt, qanats are over 3 km long, carrying water from mountain front to remote places in the valley (see figure below). Average length of qanats is 40 km, the slope between 1/100 and 3/100, and the depth up to 120 m. Mountain range Qanat 1-2 m m City B: Cross section of a qanat A: A typical qanat layout for water suypply Water intake area Vertical air shafts Farmland ~1 m ~50 m Groundwater level Aquifer (alluvial silt) Shale (impervious) Rock C: Longitudinal section of a qanat

5 Introduction 5 Examples - The Hellenic Civilization (Biswas, p ) Aristotle recommendation for research was that not all facts under the posession should be taken into account, but only a small portion of them. Therefore, many conflicting theories were advanced on almost every subject, as illustrated by the following passage: All the powers of ancient philosophy was not able to settle any one principle of nature. Thales maintain d that the water was the great source of all things; Heraclitus declar d for the fire; Anaximenes for the air; Pythagoras for numbers; Democritus for atoms; Museus for unity; Parmenides for infinity... Protagoras affirmed that every thing was really true which appear d to be so. Aristippus allow d nothing to be true but what men are thro ly convinc d of by inward perwasion of the mind. Chrysippus declares, that the senses are always in the wrong; Lucretius contends, that they are always in the right. Hippon of Samos, around the middle of the 5th century BC, deduced that all water comes from the sea. The reasoning was thus: All water that is drunk comes from the sea; for of course the wells from which we drink are not deeper than the sea, for in that case the water would not be from the sea but from elsewhere. But in fact the sea is deeper than the water. It follows therefore that all water that is above the sea comes from the sea. Examples - The Roman Civilization Marcus Vitruvius Pollio (first century BC, northern Italy) wrote a multi-volume treatise on architecture entitled De architectura libri decem. Book 8 of this treatise is devoted to water supply. One remarkable observation was that soil types provide some idea about the presence of ground water; hence, the nature of the ground should be studied carefully. Details regarding the availability of water in various types of soils are shown in Table 3. Table 3. Water in various soils. Type of soil Depth at which water may be available Amount Taste Remarks Clay Near the surface Scanty Not good --- Loose gravel Lower down the surface Scanty Unpleasant Muddy Black earth Excellent Available after winter rains Gravel --- Small and uncertain Unusually sweet --- Coarse gravel, common --- More certain Good --- sand and red sand Red rock --- Copious Good Difficult to obtain due to percolation Flinty rock and foot of mountains --- Copious Cold and wholesome ---

6 Introduction 6 Important topics in hydrogeology Source for both figures: Gleeson, T., D.M. Allen and G. Ferguson, Teaching hydrogeology: a review of current practice. Hydrology and Earth System Sciences, 16,