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Hydrology. Study of the movement and behavior of water. Hydrology. Physical, chemical, and biological attributes shaped at large and small geographic scales Probably single most important driver to large rivers – hydrological processes Must understand hydrology
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Hydrology Study of the movement and behavior of water
Hydrology • Physical, chemical, and biological attributes shaped at large and small geographic scales • Probably single most important driver to large rivers – hydrological processes • Must understand hydrology • Large rivers do not “pop up” (exceptions)
Tributary Tributary Tributary Tributary Tributary Tributary Tributary Tributary Tributary Large River
Variable Above Missouri Below Missouri Water volume 3,576 m3/s 5,923 m3/s Nitrate – N 5.7 mg/L 2 mg/L Susp. Sediment <20 mg/L 340 mg/L
Are tributaries always going to have a strong influence on receiving waters?
Water Movement – Current Velocity Lab Tuesday Readings – why older papers? are they covered in lecture – yes and no
Volume of Water Moving • Gage or Stage Height - the surface elevation or water level based on some standard • Discharge - the volume of water passing a specific point per unit time • Drainage Basin (watershed) - the total area from which water flows into a surface water channel
Amazon and Major Tributaries Dots on right denote gaging stations
Temporal Hierarchical Levels of Hydrological Behavior • Flow regime (long-term, statistical generalization of flow behavior—influences that extend over 100s of years); • Flow history (the sequence of floods or droughts—influences between 1 to 100 years); • Flood pulse (a flood event—influences that generally extend less than one year); and • Flow hydraulics (turbulence, velocity and depth—microscale influences that extend less than an hour). • Refer back to first two slides (scale)
Flow History NOTE: The 6 yr of pre-dam data were recorded during a drought period
Components of Natural Flow • Magnitude – amount of water moving past a fixed location per unit time (minimum and maximum magnitude) • Frequency of occurrence – how often a flow of given magnitude recurs over a time interval Poff et al. (1997)
Components of Natural Flow • Duration – period of time associated with a given flow event • Predictability – the regularity with which a given flow event occurs • Rate of change – the length of time from an event of one magnitude to another
Factors Shaping Hydrological Behavior • Controlled by upstream subcatchments, which have a range of: • climate • topography • geology and soils • land use • Channel, bank, floodplain storage • River-alluvial aquifer interaction • Climatic and hydrogeological diversity
Runoff – the ultimate source of water
Factors Affecting Runoff • Primary Controls • Climate • Soil Type • Bedrock Lithology • Secondary Controls • Vegetation Cover • Topography
River Regime Statistics • Average Discharge • Bankfull Discharge • Flood Discharge • Flow Duration Curve • Flood Frequency Curve