Hydrology PDF

INTRODUCTION TO HYDROLOGY References: Bedient, P., Huber, W & Vieux, B. 2012. Hydrology and Floodplain Analysis. Pearson Brutsaert, W. 2005. Hydrology, an Introduction. Cambridge University Press Karamouz, M., Nazif, S. & Falahi, M. 2013. Hyd...

INTRODUCTION TO HYDROLOGY References: Bedient, P., Huber, W & Vieux, B. 2012. Hydrology and Floodplain Analysis. Pearson Brutsaert, W. 2005. Hydrology, an Introduction. Cambridge University Press Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press HYDROLOGY – a multidisciplinary subject that deals with the occurrences, circulation, storage, and distribution of surface and ground water on the earth. The domain of hydrology includes the physical, chemical, and biological reactions of water in natural and man- made environments. Because of the complex nature of the hydrologic cycle and its relation to weather inputs and climatic patterns, soil types, topography, geomorphology, and other related factors, the boundary between hydrology and other earth sciences (i.e., meteorology, geology, oceanography, and ecology) is not distinct. Bedient, P., Huber, W & Vieux, B. 2012. Hydrology and Floodplain Analysis. Pearson Hydrology is literally the science of water. Etymologically, the word has its roots in ancient Greek, and is a composite, made up of water and word. Defined this way, the term is much too broad to be very useful, as it would have ramifications in all scientific disciplines. Through the years, with the increasing maturity of this field of endeavor, a more precise definition has emerged. Hydrology became widely accepted to be the science that deals with those aspects of the cycling of water in the natural environment that relate specifically with: 1. The continental water processes, namely the physical and chemical processes along the various pathways of continental water (solid, liquid and vapor) at all scales, including those biological processes that influence this water cycle directly; and with 2. The global water balance, namely the spatial and temporal features of the water transfers (solid, liquid and vapor) between all compartments of the global system, i.e. atmosphere, oceans and continents, in addition to stored water quantities and residence times in these compartments. Brutsaert, W. 2003. Hydrology, an Introduction. 2005. Cambridge University Press Because it is defined as being concerned specifically with continental water processes, hydrology is a discipline distinct from meteorology, climatology, oceanology, glaciology and others that also deal with the water cycle in their own specific domains, namely the atmosphere, the oceans, the ice masses, etc. of the Earth; at the same time, however, hydrology integrated and links these other geosciences, in that through the global water balance it is also concerned with the exchanges of water between all these separate compartments. Brutsaert, W. 2003. Hydrology, an Introduction. 2005. Cambridge University Press With this definition, the practical scope of hydrologic analysis is delineated in engineering and in other applied disciplines. It consists of the determination of the amount and/or flow rate of water that will be found at a given location and at a given time under natural conditions, without direct human control or intervention. Brutsaert, W. 2003. Hydrology, an Introduction. 2005. Cambridge University Press How hydrology differentiates from hydraulics. The specification, that no human control be involved, is necessary to distinguish hydrology from the related discipline of hydraulics. Hydraulics is concerned with the study of controlled fluid motion in well- defined and often in human- made environments. For instance, problems involving pipe flow, irrigation water distribution or pumping of groundwater are not hydrologic in nature, but are more properly assigned to the realm of hydraulics. Brutsaert, W. 2003. Hydrology, an Introduction. 2005. Cambridge University Press In hydrology and hydroclimatology, water science with engineering applications and the interaction of water with different mediums in the Earth- atmospheric system is studied. Water occurs on Earth in all its three states: liquid, solid and gas, in various degrees of motion. Evaporation of water from water bodies suah as oceans and lakes, formation and movement of clouds, rain and snowfall, stream flow, groundwater movement are the main topics studies in hydrology and hydroclimatology, which show the dynamic nature of water. The various aspects of water related to the Earth can be explained in terms of climatic variability in a cycle known as the hydrologic cycle. Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press Due to high interactions of water with other Earth- atmosphere components, it is necessary to manage water (in different phases) in a sustainable fashion through integrated water resources management. Water more than ever, as an important element in the formation and conservation of the environment, is receiving global attention. The main challenge is to understand the principles and laws governing the formation and movement of water in nature. Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press SYSTEMS APPROACH The study of any phenomenon, process, and/or structure such as climatic system or hydrologic cycle requires an integrated approach. The selected framework of study dictates the way an environment is dismantled for analysis. It also determines the integration of environmental components so that the results of analysis can be incorporated in a holistic fashion. For providing such a framework, understanding of system concepts is needed. Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press SYSTEMS APPROACH The Earth’s environment is composed of several systems working together in harmony but with some complex relations and interactions. For a systems approach to hydroclimatology and hydrology, it is necessary to have a clear understanding of different components of the Earth’s system and the positioning of each subsystem with respect to other subsystems. This will help understand and provide a physical interpretation of different climatic events in global and regional scales. Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press SYSTEMS APPROACH The traditional knowledge of hydroclimatology and hydrology focuses on those variables that are more tangible and representative such as temperature and its variations, wind near the surface of the Earth, humidity, cloud characteristics, precipitation in its various forms, and seasonal variability of runoff. However, these variables could not completely define the hydroclimatic and hydrologic systems and their variations that depend on different parameters such as the vertical structure of the atmosphere, the influence of the underlying land and sea, the anthropogenic activities, and many other factors that are not fully explored in many classical hydrology courses. The hydrologic cycle is a model of holistic nature and has been cited as a true system in the literature wherever examples of system integration have been brought up in art, science, and engineering. Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press  THE HYDROLOGIC CYCLE References: Brutsaert, W. 2005. Hydrology: An Introduction. Cambridge University Press  Precipitation Sublimation Interception Transpiration Surface Runoff Depression Evaporation Storage Drought Flow Water Infiltration Base Flow Percolation Vadose Zone Groundwater Aquifers Water Table Plant Uptake (confined and unconfined), Aquitard, Aquiclude  PRECIPITATION References: Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc.  INFILTRATION References: Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc.  Introduction ▪ Once net precipitation reaches the ground, it either moves into the soil, forms puddles on the soil surface, or flows over the soil surface. ▪ Precipitation that enters the soil and is not retained by the soil moves either downward to groundwater or downward and laterally along soil strata to a stream channel or other water body; this is called either effective precipitation or excess precipitation. ▪ Water flowing over the soil surface reaches the stream channel in a shorter time that that flowing through the soil. ▪ The allocation of excess precipitation at the soil surface into surface or subsurface flow determines the timing and amount of streamflow that occurs. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc.  The Basics of Infiltration ▪ Infiltration- the process by which water enters the soil surface. ▪ It results from the combined forces of capillarity and gravity acting on water in the soil matric of micropores (which relate to the size of pores attributed to soil texture) and macropores (which are larger and occur in soils as a result of several factors. ▪ Rapid infiltration rate – as a result of dry and unfrozen soil where physical attraction of soil particles to water occurs (capillarity) and the flow through macropores that are open to the atmosphere at the soil surface. ▪ Rate diminishes exponentially and eventually becomes relatively constant with time once macropores are no longer existing. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc.  The Basics of Infiltration ▪ Percolation – downward movement of excess precipitation through the soil which includes drainage from soil horizons in which soil water content exceeds the soil’s field capacity or where water flows preferentially through macropores in response to gravity. ▪ Rate at which net precipitation enters the soil surface is dependent on the following factors: 1. An upper horizon composed of stems, leaves and other undecomposed plant material. 2. A lower horizon of decomposed plant material such as litter and duff that behaves much like mineral soil. ▪ Raindrop impact can displace smaller particles into pores and effectively seal the soil surface. ▪ Thus, plant debris allows water to infiltrate. Brooks, K., Ffolliot, P. & Magner, J. 2012. Hydrology and the Management of Watersheds. John Wiley & Sons, Inc.  The Infiltration Rate ▪ The infiltration capacity or infiltration rate is the maximum rate at which water can infiltrate ▪ The actual rate will be equal to the rate of rainfall if the rainfall rate is less than the infiltration capacity. f = i if fp > i ▪ Otherwise, it will be equivalent to the infiltration capacity, and the rainwater that does not infiltrate will flow over the ground surface after filling the surface depressions. f = fp if fp < I where fp = infiltration capacity f = actual rate of infiltration i = rate of rainfall Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press  The Infiltration Rate ▪ If the infiltration is the only (or the dominating) type of abstraction ie = i – f where ie is rate of excess rainfall. ▪ Infiltration capacity depends on the : 1. soil characteristics 2. Humidity of the soil 3. Initial moisture condition Karamouz, M., Nazif, S. & Falahi, M. 2013. Hydrology and Hydroclimatology: Principles and Applications. CRC Press  The End Be sure to read the recommended reading to be able to answer the short quiz task.  INFILTRATION CAPACITY EQUATION THE HORTON METHOD Karamouz, M., Nazif, S. & Falahi, M. (2013). Hydrology and Hydroclimatology: Principles and Applications. CRC Press Calculating Infiltration Capacity HORTON METHOD Example 4.12 p.118 Example 4.12 p.118 Δ Σ Δ Σ  MODULE 8 EVAPORATION AND EVAPOTRANSPIRATION Karamouz, M., Nazif,S. & Falahi, M. (2013). Hydrology and Hydroclimatology: Principles and Applications. CRC Press THE EVAPORATION IMPORTANT A process in which a liquid changes to a gaseous state at the free surface, below the boiling point through the transfer of heat energy. LINKS IN THE EVAPOTRANSPIRATION HYDROLOGIC CYCLE Plants lose moisture by the evaporation of water from soil and water bodies. Evaporation and transpiration can be considered in one process. ASPECTS OF LOSS OF WATER VIA EVAPORATION from an open water surface, E. transpiration from vegetation, Et P ix e la s t | D e s ig n a n d T e ch  WHICH IS HARDER TO QUANTIFY? Et is more difficult to quantify since transpiration rates can vary considerably over an area and the source of water from the ground for plants requires careful definition. E AND Et VS RAINFALL The instrumental measurements of evaporation are not as simple as rainfall but the former's quantities are less variable from one season to another, thus, it is easily predicted than rainfall amounts. h MODULE 9 EVAPORATION EVALUATION Karamouz, M., Nazif,S. & Falahi, M. (2013). Hydrology and Hydroclimatology: Principles and Applications. CRC Press The template and all photos used are from canva.com  Evaluation Methods of Evaporation Quantity In calculating evaporation from open water, E, four methods are used namely: Water Budget Method Mass Transfer Method Pan Evaporation the Penman Equation  EVAPORATION EVALUATION WATER BUDGET MASS TRANSFER PAN EVAPORATION Based on hydrologic continuity The mass transfer An evaporation pan is used to equation coefficients are determined hold water during using energy- budget observations for the Problems with the method result evaporation as an determination of the quantity from errors in measuring independent measure of of evaporation at a given precipitation, inflow, outflow, evaporation location. change in storage, and subsurface seepage. Water Budget Method For lake evaporation Parameters: Change in Storage, ΔS Surface Inflow, I Surface Outflow, O Subsurface seepage to groundwater flow GW Precipitation, P E = -ΔS + I + P – O - GW Mass Transfer SIMPLE EQUATION E = f(u)(es – ed) where f(u) = function of wind speed, u es = saturated vapor pressure of air at water surface ed = saturated vapor pressure of the air at the dew point LOSS FROM A RESERVOIR E = 0.291A-0.05 u2(es – ed) where A = area in m2 u2 = speed at 2m The best known of the pans is the “Class A” evaporation pan – open galvanized iron tank Pan Evaporation 4’ diameter, 10” depth mounted 12” above ground. Pan is filled to 8” and must be refilled when level has fallen to 7”. Water surface level is measured daily, and evaporation is computed as the difference between observed levels, adjusted for any precipitation measured in a standard rain gauge E = Pan Coefficient, C p x Pan Evaporation Pan Evaporation