GIS Applications for Water, Wastewater, and Stormwater Systems - Chapter 10

CHAPTER 10 Monitoring Applications GIS is ideally suited to install, maintain, and query monitoring equipment such as, rain gauges, flow meters, and water quality samplers for system physical and hydraulic characterization. GIS allows display and analysis of monitoring data simply by clicking on a map of monitoring sites. Gauging and inspection stations in the city of Los Angeles, California. Copyright © 2005 by Taylor & Francis LEARNING OBJECTIVE The learning objective of this chapter is to familiarize ourselves with GIS applications in monitoring data for effective operation and management of water, wastewater, and stormwater systems. MAJOR TOPICS · Rainfall monitoring · Satellite and radar rainfall data · Flow-monitoring applications · Permit reporting applications · Internet monitoring applications · Infrastructure monitoring applications LIST OF CHAPTER ACRONYMS CCTV Closed Circuit Television GML Geography Markup Language HRAP Hydrologic Rainfall Analysis Project (a map projection system) NCDC National Climatic Data Center (U.S.) NEXRAD Next Generation Weather Radar NOAA National Oceanic and Atmospheric Administration (U.S.) NPDES National Pollution Discharge Elimination System (U.S.) NWS National Weather Service OGC Open GIS Consortium SCADA Supervisory Control and Data Acquisition Systems WSR Weather Surveillance Radar This book focuses on the four main applications of GIS, which are mapping, monitor-ing, modeling, and maintenance and are referred to as the “4M applications.” In this chapter we will learn about the applications of the second M (monitoring). MONITORING REAL TIME RAINFALL AND STREAM-FLOW DATA IN AURORA The city of Aurora, Colorado, is a community of approximately 247,000 people located in the southeast Denver metro area. The City’s Utilities Department used ESRI’s ArcInfo and ArcView software to analyze and display real time rain-gauge and stream-flow data from the City’s ALERT Flood Warning System. Data were obtained by querying a remote real time data-collection database. The Utilities Department was able to access and analyze both historical and current real time rainfall and stream-flow data from an easy-to-use graphical interface. ArcView’s Spatial Analyst Extension was used to develop a continuous areal rainfall surface from the point rainfall data. This allowed a better and clearer understanding of a particular storm and allowed a Copyright © 2005 by Taylor & Francis more complex analysis of the true impact of the storm event. Applications of this program included studies in emergency flood response, location of flood reports, routine maintenance for storm sewers, and National Pollution Discharge Elimination System (NPDES) compliance for water quality (Rindahl, 1996). MONITORING BASICS Monitoring of various types of data is essential to the effective management of water, wastewater, and stormwater systems. Generally, two types of data are required: (1) physical characterization data and (2) hydraulic characterization data. Physical characterization data describe the physical condition of the infrastructure, such as pipe and manhole conditions. Examples of physical characterization data sources include closed-circuit television (CCTV) inspection of pipes, manhole inspections, and smoke-testing of buildings. GIS applications for these types of data are described in Chapter 15 (Maintenance Applications). Hydraulic characterization data describe the quantity and quality of flow through pipes and open channels as well as meteorological factors impacting the flow, such as precipitation. Wastewater and stormwater systems typically require data on flow quantity (depth, velocity, flow rate, and volume), quality (e.g., suspended solids and bacteria), and rainfall. Figure 10.1 shows a flowmeter and weir installation in a combined sewer system overflow manhole. The flowmeter (Flo-Dar from Marsh-McBirney, Inc.) shown on the left records incoming combined sewage depth, velocity, and flow data. The weir shown on the right collects outgoing overflows. Some wastewater and stormwater hydrologic and hydraulic (H&H) models require data on addi-tional meteorological parameters such as ambient temperature, evaporation rate, and wind speed. Water distribution systems typically require water pressure and water quality data. In many projects, monitoring tasks make up a significant portion of the scope of work and could cost 20 to 30% of the total budget. Careful installation of monitors and effective management of monitoring data is, therefore, highly desirable for the on-time and on-budget completion of monitoring projects. GIS is ideally suited for selecting the best sites for installing various hydraulic characterization monitors. Once the monitors have been installed, GIS can be used to query the monitored data simply by clicking on a map of monitoring sites. GIS can also be used to study the spatial trends in the monitored data. GIS is especially useful in processing and integrating radar rainfall data with H&H models of sewage collection systems and watersheds. This chapter will present the methods and exam-ples of how to use GIS for installing and maintaining the monitors, and for querying and analyzing the monitoring data. REMOTELY SENSED RAINFALL DATA Many watersheds, especially those smaller than 1000 km2, do not have recording rain gauges capable of recording at hourly or subhourly intervals. Sometimes rain gauges exist, but data are found missing due to equipment malfunction. Quite often, Copyright © 2005 by Taylor & Francis Figure 10.1 Flowmeter and weir installation in a manhole for monitoring incoming and out-going flows. rain-gauge density is not adequate to accurately capture the spatial distribution of storm events. Such data gaps can be filled by the rainfall data provided by weather satellites and radars, as described in the following subsections. Satellite Rainfall Data Direct measurement of rainfall from satellites is not feasible because satellites cannot penetrate the cloud cover. However, improved analysis of rainfall can be achieved by combining satellite and conventional rain-gauge data. Meteorological satellites such as the NOAA-N series, those of the Defense Meteorological Satellite Program, and U.S. geostationary satellites can observe the characteristics of clouds with precipitation-producing potential and the rates of changes in cloud area and shape. Rainfall data can now be estimated by relating these cloud characteristics to instantaneous rainfall rates and cumulative rainfall over time. Cloud area and tem-perature can be used to develop a temperature-weighted cloud cover index. This index can be transformed to estimate mean monthly runoff values. Satellite rainfall estimating methods are especially valuable when few or no rain gauges are available (ASCE, 1999). Copyright © 2005 by Taylor & Francis Radar Rainfall Data Weather radars provide quantitative estimates of precipitation, which can be used as input to H&H models. Radar rainfall estimates augmented with data from sparse rain-gauge networks are useful in H&H modeling. Weather radars provide real time, spatially distributed rainfall data that can be extremely valuable for flood forecasting and flood warning. NEXRAD Rainfall Data The U.S. National Weather Service (NWS) has a group of weather radars called the Next Generation Weather Radar (NEXRAD) system. NEXRAD comprises approximately 160 Weather Surveillance Radar–1988 Doppler (WSR-88D) sites throughout the U.S. and selected overseas locations. This system is a joint effort of the U.S. Departments of Commerce (DOC), Defense (DOD), and Transportation (DOT). The controlling agencies are the NWS, Air Weather Service (AWS), and Federal Aviation Administration (FAA), respectively. Level II data provide three meteorological base data quantities: reflectivity, mean radial velocity, and spectrum width. These quantities are processed to generate numerous meteorological analysis products known as Level III data. Level II data are recorded at all NWS and most AWS and FAA WSR-88D sites. Level III products are recorded at the 120 NWS sites. The data are sent to the National Climatic Data Center (NCDC) for archiving and dissemination. NEXRAD Level III Data There are a total of 24 Level III products routinely available from NCDC, including 7 graphic products in clear-air mode, 11 in precipitation mode, 5 graphic overlays, and 1 alphanumeric product. Each product includes state, county, and city background maps. Level III graphic products are available as color hard copy, grayscale hard copy, or acetate overlay copies. A brief description and possible uses of these products are given below: · Base Reflectivity (R): A display of echo intensity measured in dBZ (decibels of Z, where Z represents the energy reflected back to the radar). This product is used to detect precipitation, evaluate storm structure, locate boundaries, and determine hail potential. · Base Spectrum Width (SW): A measure of velocity dispersion within the radar sample volume. The primary use of this product is to estimate the turbulence associated with mesocyclones and boundaries. · Base Velocity (V): A measure of the radial component of the wind either toward the radar (negative values) or away from the radar (positive values). Negative values are represented by cool colors (green), whereas positive values are repre-sented by warm colors (red). This product is used to estimate wind speed and direction, locate boundaries, locate severe weather signatures, and identify sus-pected areas of turbulence. Copyright © 2005 by Taylor & Francis ... - tailieumienphi.vn