Department of Civil Engineering Geographical Information System Project
"Wadi Al zarqa" Hydrology Analysis for Watershed
Done by: Yazan Rafiq Al Haddad
20102023117
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Table of content………………………………….………………………………………..1 1.0 GIS?.............................................................................................2 1.1 What is GIS??................................................................................2 1.2 Defining GIS………………………………………………………………………….....2
2.1 Al-Zarqa River……………………………………………………………………………3
3.0 Hydrology………………………………………………………………………………….4 3.1 Watershed…………………………………………………………………………………4 3.2 Watershed Characteristics……………………………………………..……………5
4.0 Hydrology Analysis On Arc_GIS…………………………………………………….6 4.1 Export Data…………………………………………………………………………………6 4.2 Hydrology analysis……………………………………………………………………….8 References…………………………………………………………………………………..15
1.1 What is GIS? Geographic Information System (GIS) is a computer based information system used to digitally represent and analyze the geographic features present on the Earth' surface and the events (non-spatial attributes linked to the geography under study) that taking place on it. The meaning to represent digitally is to convert analog (smooth line) into a digital form. "Every object present on the Earth can be geo-referenced", is the fundamental key of associating any database to GIS. Here, term 'database' is a collection of information about things and their relationship to each other, and 'geo-referencing' refers to the location of a layer or coverage in space defined by the co-ordinate referencing system. Work on GIS began in late 1950s, but first GIS software came only in late 1970s from the lab of the ESRI. Canada was the pioneer in the development of GIS as a result of innovations dating back to early 1960s. Much of the credit for the early development of GIS goes to Roger Tomilson. Evolution of GIS has transformed and revolutionized the ways in which planners, engineers, managers etc. conduct the database management and analysis.
1.2 DEFINING GIS A GIS is an information system designed to work with data referenced by spatial / geographical coordinates. In other words, GIS is both a database system with specific capabilities for spatially referenced data as well as a set of operations for working with the data. It may also be considered as a higher order map. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public and private enterprises for explaining events, predicting outcomes, and planning strategies. A Geographic Information System is a computer based system which is used to digitally reproduce and analyse the feature present on earth surface and the events that take place on it. In the light of the fact that almost 70% of the data has geographical reference as it's denominator, it becomes imperative to underline the importance of a system which can represent the given data geographically. A typical GIS can be understood by the help of various definitions given below -: ďż˝ A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on Earth ďż˝ Burrough in 1986 defined GIS as, "Set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes " ďż˝ Arnoff in 1989 defines GIS as, "a computer based system that provides four sets of capabilities to handle geo-referenced data . 2
2.1 Al-Zarqa River The Zarqa River is the second tributary to River Jordan (after Yarmouk River) and is considered the most important one as it host more than half of the population of Jordan as well as most of the industrial and agricultural activities. The basin has two distinguished hydrological relief; the Wadi Dullail sub-basin which has a semi arid characteristics and gentle relief where most of the flood water originates. The second group of relief is the mountainous sub-basins which they have sub-humid climate and drain flood and base flows. The basin has an area of 4128 Km3, including the Jordan Valley sub-basin, and extends from upper northern point in Jabal al-Arab in Syria at an elevation of 1460 m (amsb) to the lower west southern point in the Jordan River at an elevation of -360 (bmsl). The flood and the base flows of the river is intercepted by King Talal Dam with a total capacity of 85 MCM. The water of the dam is considered a major source of irrigation water in the Jordan Valley.
Sub-basins hydrological characteristics of Zarqa River basin have been evaluated in terms of relief, slope length of the reach and hydrological soil grouping. Comparative study was carried out to evaluate the rainfall-runoff relationship using different hydrological models. These models are: the simple linear model (SLM), the linear variable gain factor model (LUGFM), the non-linear model (NLM), the water modeling system (WMS) and the rainfall-runoff model of WaterWare system (RRM). Linear decision rule was applied to determine the reservoir management and capacity by analyzing the monthly flow and seasonal flow pattern in order to determine the release commitment downstream.
The basin is going under different activities including agriculture, urbanization, industrialization and soil conservation measures. The impact of these activities was monitored in order to evaluate their effect on the hydrological characteristics of the watershed. Different measures and policies were suggested for the optimization of land and water resources of Zarqa River Watershed.
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3.0 Hydrology Where hydrology is a field of engineering that applies the concept of fluid mechanics to deal with the measurement, transport and storage of water, hydrology in contrast is a science that involves the study of the properties, movement and circulation of earth's water. A major application of hydrology is the determination of the peak discharge resulting from a storm event.
3.1 Watershed The watershed is the basic unit of all hydrologic analysis and designs. Any watershed can be subdivided in to a set of smaller watersheds. Usually a watershed is defined for a given drainage point. This point is usually the location at which the analysis is being made and is referred to as the watershed “outlet�. The watershed, therefore, consists of all the land area that drains water to the outlet during a rainstorm. The boundary of a watershed therefore consists of the line drown across the contours joining the highest elevations surrounding the basin. Watersheds considered in engineering hydrology vary in size from a few hectares in urban areas to several thousand square kilometers for large river basins. Figure 1 shows the delineation of a watershed boundary. A common task in hydrology is to delineate a watershed from a topographic map. To trace the boundary, one should start at the outlet and then draw a line away on the left bank, maintaining it always at right angles to the contour lines. (The line should not cross the drainage paths) Continue the line until it is generally above the headwaters of the stream network. Return to the outlet and repeat the procedure with a line away from the right bank. The two lines should join to produce the full watershed boundary. In recent years the use of GIS (Geographic Information System) has become increasingly popular and has facilitated much of the work of hydrologists. The use of DEMs (Digital Elevation Models) in particular has made watershed delineation a relatively smooth procedure. Watershed Geomorphology Watershed geomorphology refers to the physical characteristics of the watershed. Certain physical properties of watersheds significantly affect the characteristics of runoff and as such are of great interest in hydrologic analyses. The principal watershed characteristics are: Area of the watershed: The area of watershed is also known as the drainage area and it is the most important watershed characteristic for hydrologic analysis. It reflects the volume of water that can be generated from a rainfall. Thus the drainage area is required as input to models ranging from simple linear prediction equations to complex computer models. Once the watershed has been delineated, its area can be determined, either by approximate map methods or by GIS.
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3.2 Watershed Characteristics 3.2.1 Length of watershed: Conceptually this is the distance traveled by the surface drainage and sometimes more appropriately labeled as hydrologic length. This length is usually used in computing a time parameter, which is a measure of the travel time of water through a watershed. The watershed length is therefore measured along the principal flow path from the watershed outlet to the basin boundary. Since the channel does not extend up to the basin boundary, it is necessary to extend a line from the end of the channel to the basin boundary. The measurement follows a path where the greatest volume of water would generally travel. 3.2.2 Slope of watershed: Watershed slope affects the momentum of runoff. Both watershed and channel slope may be of interest. Watershed slope reflects the rate of change of elevation with respect to distance along the principal flow path. It is usually calculated as the elevation difference between the endpoints of the main flow path divided by the length. The elevation difference may not necessarily be the maximum elevation. 3.2.3 Shape of Watershed : Basin shape is not usually used directly in hydrologic design methods; however, parameters that reflect basin shape are used occasionally and have a conceptual basis. Watersheds have an infinite variety of shapes, and the shape supposedly reflects the way that runoff will “bunch up� at the outlet. A circular watershed would result in runoff from various parts of the watershed reaching the outlet at the same time. An elliptical watershed having the outlet at one end of the major axis and having the same area as the circular watershed would cause the runoff to be spread out over time, thus producing a smaller flood peak than that of the circular watershed.
Fig(3.a) Al-Zarqa River
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4.0 Hydrology Analysis on ArcGIS In this part of our project we studied the water shade of Al-zarqa River; therefore we found the area and slop of this watershed, which is important to know the region around the river or the valley that received to them water from runoff which is occur from precipitation, addition slop of water shade give us the direct of flow from the highest points in topographically to lower point, that's create what we call streams (sub-basin) and then they flows to main stream.
4.1 Export Data 1st we should export the Digital Elevation Model (DEM) and connect it with arc catalog as illustrated in figure 4.a , DEM important to show the topographical feature of land or region we want to use. The alternate of DEM is Google earth program, it's used for places we haven't information about them. In the Arc Map we can show DEM on map display by add the file and the layer will appear on table of content.
Fig. (4.1)
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When the DEM of Jordan will appear on map display with the map for valleys, that illustrated in the figure below , it’s important to determine approximately the region that will work on it, this step specify the only region you will make your studies, for example we need just the stream line that contact with the major stream. By using Spatial Analyst tools > Extraction > Extraction by Mask. You can extract the area you want to work on.
Fig. (4.2a)
Fig. (4.2b)
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4.2 Hydrology analysis We analyzed the hydrology of the river using the hydrology tool box extension from Arc tool box. Like, flow direction, Flow accumulative, stream link, stream order.
Fig. (4.3 a) dialog for flow Direction.
Fig. (4.3 b) dialog for flow accum.
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After we made the step before (flow direction & flow accumulative), in map display will appear polygon with these flow lines or stream that is specific for this area, such that illustrated in figure (4.4).
These processes are depending on each other, because if we do any process it will depend on the previous one, like in previous figure, in first blank on flow accumulative dialogue we put "flow direction" layer, that depending in what’s done previously, therefore step by step in GIS we getting more and more specified property of what we want.
Fig. (4.4)
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Important thing that we should do are: 1- determine where is the end point of stream or outlet point (pour point) 2- and then doing the watershed for polygon as illustrated in figure below.
Fig. (4.5)
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This result showen in figure below will happen after insuring the water shade dialogue cotent. As seen below the boundary of watershed of wadi al zarqa became specificly more than the polygon that we made, and that's better of course ,because it minimize the area that not important for me.
Fig. (4.6)
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In figure below, all streams that related to watershed are within boundary. These streams affect on the outlet volume of water, and water that passes through main stream.
Fig. (4.7)
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There is important step to do is to conversion the feature to raster, that makes calculation of watershed area possible. from select feature tool, selecting the raster and then from attribute table we can calculate the area in "hectaer" as seen below in figure .
Fig. (4.8)
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The last thing is to finding the slope of watershed for the "raster", and the different in color indication of change in slope due to the kind of land. As it's appear below, the dark green indicates that there are no slope when color convert to yellow, the slope is found and the red color indicates to deep slope.
Fig. (4.9)
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References -Getting to know ArcGIS desktop book -wikipedia - Office for Information ResourcesGIS Services - Indian Institute of Information Technology
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