What is the Sewer Datasource and what can it do for me?
The Sewer Datasource is a virtual data source which can be accessed from any HYDSTRA program. It acts a software layer which sits above sewer data from multiple velocity and depth transducers, but which also takes into account physical aspects of the configuration of the monitoring location such as pipe shape and silt depth to compute depth, flow and other useful parameters. It can be used in conjunction with some powerful sewer-specific features of HYAUDIT to report a range of sewer-specific indicator variables such as peak dry weather flow, silt depth as a percentage of conduit height, catchment runoff as a percentage of total rainfall, etc.
What are the major components of the Sewer Datasource?
The Sewer Datasource requires that a number of components be in place before you can start asking for datasource data:
DATASRC.INI needs to be configured to make a sewer datasource available - this will be a one-off task.
SEWER.INI needs to be configured to specify the variable numbers and units you are planning to use. This will also be a one-off task.
The SEWRSITE and SEWRCONF databases need to be set up. These must have entries for each site you wish to analyze. SEWRCONF may need many entries at different date and times, and accounting for changes in the logger setup, changes in silt depth, upstream population, etc.
The Cross Sections system needs to have a cross section defined for the site. You can use HYCHANNL to create the cross section, or you can simply enter the surveyed section coordinates into the SECTIONS database manually.
You need clean edited time-series data for the site. You can have up to four depth velocity or flow traces, and you can calculate any one of these variables from the other two by a variety of methods (specified in SEWRCONF)
Once you have all these elements in place you can start using the sewer datasource from any HYDSTRA program, including HYPLOT, HYAUDIT and MODSYN.
How do I set up DATASRC.INI?
DATASRC.INI needs to be set up to access the sewer datasource from normal programs. An example line in DATASRC.INI such as:
S? = SOURCE=SEWER,SUFFIX=?,Text=Sewer Datasource
This line specifies that any datasource starting with 'S' is a sewer datasource, and that any time-series data will come from the time-series file with the second letter as suffix. Thus 'SA" will look for any time-series data it needs in the 'A' or archive file, while 'SZ' would look in a work file with Z suffix.
DATASRC.INI is delivered in MISCPATH, but you must not edit it there. If you need to edit DATASRC.INI, copy it to INIPATH first, and edit it there.
If you make changes to DATASRC.INI, don't forget to run HYMKHELP to update the dropdowns which appear in all programs which support data sources:
How do I set up SEWER.INI?
SEWER.INI needs to be set up with variable numbers to match your installation. An example SEWER.INI is shown below:
[VERSION]
Version=1
; .used by HYAUDIT and other sewer programs
; This INI file holds default values for specific sewer related programs.
; One major user are the HYAUDIT tests which relate to sewers
[Units]
; This section specifies the reporting units used by the HYAUDIT sewer tests.
; Fill in after the '=' with valid unit codes.
Depth = M
Velocity = MS
Flow = LS
InflowRate = LS
InflowVolume = M3
Rainfall = MM
PipeLength = KM
InchMile = CMKM
; Here are a set of dimensionally-equivalent imperial units.
;Depth = FOOT
;Velocity = FTS
;Flow = FS
;InflowRate = FS
;InflowVolume = FT3
;Rainfall = PT
;PipeLength = MILE
;InchMile = INMI
[Variables]
; 'base' variables, used by the data source
; NB: these must all be unique, as they are used to 'connect' the
; user's data request (ie, VarFrom) with the category-defined
; data stream that the sewer datasource is able to provide.
DepthVar = 170
VelocityVar = 175
DischargeVar = 840
ManningsNVar = 100
ColebrookKVar = 846
; The sewer data source only returns inflow rate, but some of the HYAUDIT
; sewer tests require inflow volume.
InflowVolume = 842
The content of SEWER.INI, particularly the [Variables] section, is very important, as it defines a set of variables which you may ask of the sewer datasource. It is important to keep clear in your mind the idea that the datasource is a software layer above your time-series files, and it can derive variables that you don't necessarily have in your time-series files. The keywords in the [Variables] section enumerate all the possible different things you can ask of the sewer datasource, and the variable numbers on the right hand side specify how you ask for them.
Just to reiterate the key point here - you can ask for variable 170.02 (using the above SEWER.INI) in any time-series program, - HYPLOT for example, and you will receive a virtual time-series of silt depths from the datasource. In fact the silt depths come from some database entries in SEWRCONF, and you don't have a tine-series file of them at all - but that is what the datasource is for, to compute and extract things that aren't necessarily simple to generate in other ways.
Similarly you can ask for variable 170 and you will get depth, as calculated by the 'Depth Method' keyword in SEWRCONF. In all probability you will be calculating depth by taking the mean of a number of depth transducers. Note however that the 170 delivered by the sewer source is different to accessing any of the individual 170.01, 170.02 traces from the time-series file. The Sewer Datasource layer computes the mean for you, on demand, using the latest available edited data.
How do I set up SEWRSITE and SEWRCONF?
The last part of the jigsaw you need to put in place are SEWRSITE and SEWRCONF. These two tables are accessed through the SEWRSITE manage. You may need to uncheck the 'Profile' checkbox on the menus in order to see the 'HYDSTRA Sewer Programs' menu entry if it has not already been made available on your site. If the sewer programs are normally not visible you should use the MENUS manage to remove any profile letters from the 'SEWR' entry in USRMENUS.
SEWRSITE contains site-specific setup information. Most of the information should be fairly obvious. The cross-section information is particularly important, as many of the flow calculations rely on the cross-section. Note that the site and section number of the cross section are entered. This allows you to use a dummy site for common sections such as a 30cm pipe, rather than having to store multiple copies of the section at each site.
The silt depth, catchment area and catchment population are default values, and they can be overridden by specific values in SEWRCONF if they change over time.
SEWRCONF holds a series of date and time-stamped records which specify how to compute various parameters from that date forward. It also allows you to record changes in silt depth, roughness, etc.
How should I fill in 'Depth Method', 'Velocity Method' and 'Discharge Method' in SEWRCONF?
That depends on what measuring technology you have in place. Probably the most common sewer monitoring configuration has one or more depth transducers and one or more velocity transducers. In this situation you would probably use MEAN as the calculation method for depth and velocity. This will take the mean of all the depth and velocity variables specified in SEWRCONF. If you have only one depth transducer, specify its variable number as the first depth variable and leave all the rest zero. If you have four velocity transducers, specify the variables of the four velocity variables (e.g. 175.01, 175.02, 175.03, 175.04).
Under this scenario you probably want to compute discharge by the CONTINUITY method (discharge=area*velocity).
Some sophisticated monitors actually record discharge directly using a profiling acoustic Doppler technology,. In this case you probably would use MEAN for the discharge method as well. If the transducer returned only discharge and depth you could even calculate velocity using the CONTINUITY method, which would backsolve the continuity equation for velocity.
I have four velocity sensors, but one of them is clearly malfunctioning
Put another entry in SEWRCONF at the time the malfunction started, and specify only the transducers you want to use in your MEAN calculations, e.g. (e.g. 175.01, 175.03, 175.04).
It is always best to copy the previous SEWRSITE forward to a new data, so that it carries forward everything. Then just make the changes you want at the new date and time.
If the malfunctioning transducer is ever fixed, put in another SEWRCONF record at that date including it in the mean calculations again.
How is silt depth taken into account?
When a site is set up the SEWRSITE entry specifies a cross-section, which must be in the Cross Sections system. The cross section is immediately analyzed geometrically, and a table of depth vs area is computed. Silt depth is put through this table to compute the cross sectional area of the silt. When water depth is put through the same curve later to compute area under water, the area under silt is subtracted.
OK, I have everything set up - how do I use it?
Well you can start by running HYPLOT to plot things. For example, if you wish to plot the mean depth of all the four depth transducers, and want to use data from the 'A' or archive file, specify the site, and in the 'suffix' field on HYPLOT specify the sewer datasource SA. The variable number to ask for is the variable number from SEWER.INI against DEPTHVAR. Note that this may not necessarily be the same as the variable numbers of the raw depth traces, although in most cases it will be, though probably without a subvariable (e.g.175.00). The variable number you ask for is looked up in SEWER.INI, and the corresponding sewer datasource parameter is calculated, using the calculation method specified in SEWRCONF.
If you want to plot flow, use 'SA' and the variable from SEWER.INI against DISCHARGEVAR. It will calculate discharge using the method from SEWRCONF.
Because SEWRCONF is keyed by date, it is even to change methods for calculating flow from time to time. For example, if you lost all the velocity sensors for a period you could switch to a rating table or a Mannings method for a while, then switch back to continuity once the sensors had been repaired.
The most powerful reporting facility for sewer data is HYAUDIT, which has a variety of sewer-specific reporting facilities.
I still don't quite understand what variables I can ask for?
In a nutshell, you can only ask for the variables defined in the [Variables] section of SEWER.INI. Any other variable you ask of the datasource will not be available.
What is the relationship between the 'SA' datasource and the 'A' archive file?
The sewer datasource is defined in DATASRC.INI as S?, which means that anything starting with S is a sewer datasource. The second letter of the datasource specifies which time-series archive file is to be used, so SA will use the A archive file, SB will use the B work file, etc.
So how do I plot the individual recorded velocity traces and the mean velocity computed by the datasource?
Simple - use normal suffix 'A' and the variable numbers from the data file for the raw traces, and 'SA' and the variable in SEWER.INI for the computed mean.
So what role does HYAUDIT play in sewer analysis?
HYAUDIT is an important component of working with sewers in HYDSTRA. HYAUDIT can compute a range of interesting indicator variables which relate to sewers. The things you can compute are enumerated in HYAUDIT.INI under the [Sewer List] section. These test rely on the sewer datasource being configured correctly, and many of them consult SEWER.INI directly as well.
[Sewer List]
; this sample list is of all the sewer audit tests
Test = QFull
Test = Any Surcharge
Test = Dry Weather Surcharge
Test = Peak Dry Weather Flow
Test = Peak Dry Weather Flow > N% QFull
Test = Peak Dry Weather Flow / QFull
Test = Peak Wet Weather Flow / Peak Dry Weather Flow > N
Test = Peak Dry Weather Velocity
Test = Peak Dry Weather Velocity < N
Test = Average Dry Weather Flow
Test = Average Dry Weather Velocity
Test = Peak Dry Weather Depth / Conduit Height
Test = Peak Wet Weather Depth / Conduit Height
Test = Silt Depth > N% Conduit Height
Test = Silt Depth as % of Conduit Height
Test = No. Days of Dry Weather Surcharge
Test = No. Days of Wet Weather Surcharge
Test = Total Rainfall
Test = Peak 24 Hour Rainfall
Test = Catchment Runoff as % of Total Rainfall
Test = Inflow Volume as Catchment Runoff
Test = Inflow Volume
Test = Inflow Rate per Head of Population
Test = Inflow Rate per InchMile of Pipe
Test = Inflow Rate per Length of Pipe
HYAUDIT can print a report showing any of the above variables in columns across the page:
HYAUDIT V42 Output 26/10/1999
STATION QFull Surcharge Dry PDWF PDWV ADWF ADWV PDWD/CH PWWD/CH SD as Peak Runoff
(l/s) Surcharge (l/s) (m/s) (l/s) (m/s) % of Rainfall as % of
CH (mm) Rainfall
-------- ----- --------- --------- ----- ----- ----- ----- -------
HYDSTRA02 70 True False 70.37 1.403 16.05 0.714 0.515 16.62 1.067 111.47 0.014
-------- ----- --------- --------- ----- ----- ----- ----- -------
Because HYAUDIT can be run across a group of stations, reports of the type shown above can be quickly generated for all stations in a catchment.
I like the HYAUDIT sort of report, but I want a line for each rainfall event rather than one line for the whole period
HYAUDIT can be configured to produce a report line for each event. To do this you need to configure up a special event test, and part of the even test is to specify an event variable. An event variable is similar to a wet/dry day indicator variable. In simple terms, if the value of the event variable is non-zero, the event is 'on'; if the value of the event variable is 0, the event is 'off'. You can use all sorts of variables and datasources to serve as your event variable. Here are some ideas:
Use a time-table datasource to access a time table which manually specifies a 1/0 type variable specifying when events start and end.
Use MODSYN to compute an event variable and store it back into the file. For example, compute the antecedent rainfall using the MODSYN AWI function and declare events to start when the awi exceeds a certain value, and to stop when it falls below a certain value.
Use a variable conversion on the level to have events start when the level exceeds a threshold, and stop when it falls below the threshold.
Use MODSYN to compute a moving rainfall total
Copy one of the raw data traces to another variable, and use the Data Managers Workbench to delete or set to zero periods between events. Then use that variable as an event variable.
Some of the HYAUDIT test report wet day/dry day data. Does the datasource do wet/dry separation automatically?
No, you need to use some other HYDSTRA tools to do the separation. One simple approach is to use HYINFILT to do the separation, and store the resulting separated data back into the file. More complex approaches may require MODSYN.
Does HYDSTRA have any programs to compute flows through wet wells?
Yes, program HYPUMP can compute inflows and outflows from wet wells. It takes some setting up, as it uses databases to hold configuration information about well geometry.
What other programs are useful in working with sewers?
The ones you might like to look at include HYINFILT, HYDRY, HYSEWPL
