WRIS HMS DATABASE

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The HMS database of WRIS contains static, semi-static and non-static data in the form of separate oracle tables. Static and semi static parameters are entered in oracle master information table and non-static data is covered in separate tables for each attribute varying with time.

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• 1 Static and Semi Static Data
  • 1.1 Station characteristics
  • 1.2 Station Identification Code
  • 1.3 Location
  • 1.4 Reference Topo sheet Number
  • 1.5 Owner Agency
  • 1.6 HIS Agency
  • 1.7 Controlling Offices
  • 1.8 Site Details
  • 1.9 Establishment Details
  • 1.10 Station Categorisation
• 2 Non-Static Data
  • 2.1 Time Interval Code
  • 2.2 Time Labels
  • 2.3 Data Limits

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Attributes associated with the observational stations or equipment, which do not change with time, are considered as static type of data. Some of these attributes change but very infrequently and are thus taken to be of semi-static nature. Database stores the characteristics associated with the observation stations, data series, reduced level of gauge zero and current meters so that the same is available for reference and querying subsequently.

Many important attributes to each observational station can be assigned for defining its location in terms of geographical, administrative or drainage units and for indicating various offices which have control on its operations. Locational attributes are important for the purpose of finding inter station distances and difference in altitudes for the purpose of data processing. These characteristics are also very important for the purpose of retrieval of data pertaining to particular range of these attribute(s).

Station identification code is the unique code assigned to every station. This is the most important field of the database since most of the information in the database is associated with the observational stations and these stations are identified by this code. No two stations can have identical station identification code.

The location of a station is of prime importance in locating any observation station on the map. The location of a station is specified by entering the geographical co-ordinates in terms of latitude and longitude. The latitude and longitude is expressed in hexadecimal units, called degrees. Degrees are subdivided into minutes (1 degree = 60 minutes) and minutes into seconds (1 minute = 60 seconds).

While working with the maps, it is required to know the serial number of map on which the observation station can be located. This information is stored in the database and thus can be retrieved for a ready reference. There are unique serial numbers allotted to each of Survey of India topo sheets on the scale of 1:50,000 and the same is used to provide this reference topo sheet number. The format of this topo sheet number is nnA/NN where acceptable range, for topo sheets covering the main land of the country, of nn is an integer from 38 to 92, A is an alphabet from A to P and NN is an integer from 1 to 16.

The owner agency is the agency, which owns the observational stations. The data may be collected from these observational stations and processed by other agency.

The agency is the agency, which is receiving data from observational stations belonging to various owner agencies and is entrusted with its validation, processing and dissemination.

Apart from the name of the main HIS agency, there are other offices which have the responsibility of processing of data. All possible levels of controlling offices in the form of (a) Regional, (b) Circle, © Divisional, (d) Sub-divisional and (e) Sectional offices can be entered for an observation station. The list of all offices pertaining to any agency is readily provided to the user for making the entry by way of selecting the required one.

It is very useful to keep detailed information on the locational aspects of the observation station. This facilitates anyone who would like to visit the station for purpose of inspection or otherwise. Complete information on the station’s location with respect to the surrounding area/river, its accessibility conditions can be entered separately. Full details about the station setup with respect to equipment availability and installation can be indicated. Input fields are provided for entering the general information about address, nearest town and transport facilities.

Several important dates with respect to the establishment of the station can be associated with the station. Start date marks the establishment of the station. In case the station is closed down then the end date can be entered to show the date of closure. Several other dates for starting and closure of important observational activities like water level by manual means, water level by automatic equipment, discharge observation in general, discharge observation using current meters, observations on sediment and water quality variables. Similarly, the dates of initiating the rainfall and climatic observation by manual or automatic means can also be entered. Together with the dates there are check boxes available against each of these items. For certain types of data, like on stage-discharge, climate and water quality, it is mandatory to check these boxes for allowing the data to be entered. Thus all those stations for which stage-discharge data, climatic data and water quality data is to be entered are to be essentially checked in the boxes against such items under the establishment details tab. Only those stations, which have been registered in this manner for the required data types (stage-discharge, climate, and water quality) would appear in the respective data entry forms. A note on station history gives detail about the establishment of the station and other important maintenance, construction or installation activities carried out subsequently.

It is useful to categorise different types of observation stations in a few classes so that information belonging to a particular class can be easily used, displayed or retrieved. There are two levels of categorization:

1. Category
2. Sub-category

First, the category and sub category of the station has to be specified from among three types:

1. Surface water- G, D, S, Q, Snow
2. Meteorological- Rain fall,Climate
3. Water Quality- Q

It is possible to have simultaneous selection of both “Surface water” and Meteorological category implying thereby that the station is of river gauging type which also has meteorological observatory for observations on certain meteorological variables. Category of Water Quality can also be chosen simultaneously with Surface water and/or Meteorological type of station category. Whenever a station is also chosen as Water quality station, it implies that water quality monitoring is being done at that station. However, it is not possible to choose only water quality as the category since any station for which water quality is monitored must either be surface water or meteorological station and has to be essentially chosen.Since the category is an indication of the type of station in a very broad sense only, the subcategory of the station is important to know as what is the exact nature of the station.

The bulk of hydrological and hydro-meteorological data is time series data. At every station a number of variables are observed and sometimes at varying time intervals. Thus, the time series data is required to be organised in different series at every station for each combination of the required variables and time intervals of observation. These series are attributed with certain key characteristics, which are useful for identification and providing necessary information about the series and in validation of the elements of the series. Any time series can be recognised by its series identification code.

The bulk of hydrological or hydro-meteorological data comprise of the time series data. Depending upon the variation of time interval between various observations the time series can be of three different types: equidistant, cyclic and non-equidistant.

For an equidistant time series all the data points are spaced equally in time (in terms of calendar or time units). Whereas the time interval between the data points in the non equidistant series is not uniform. The cyclic series is the one for which, though two or more adjacent time intervals may not be identical but there is a perfect repetition or recurrence of the set of these unequal time intervals. The time interval, say t, represents:
(a) time distance between successive series elements of instantaneous observations, or
(b) time span of an accumulative observation. The time interval can be year, month, day or hour or a part thereof. The calendar units vary with time according to the Gregorian calendar.

Apart from time interval code, time labels are required for defining the time intervals between the consecutive data points. Time labels for the cyclic data series gives the exact timings at which the observations have been made in the time interval unit. It is to note here that the number of time labels is equal to that of the divider. However, for practical purpose this is limited to defining up to six time labels for a series. The time labels for the above example of two observations daily (at 0830 and 1730 hrs.) will be:

Every series is attributed with a few data limits, which are important in applying data entry checks and subsequently while screening the data for doubtful values. Since, most of the hydrological and meteorological variables are result of some physical process they are expected to occur or vary within certain limits. Though, these limits cannot always be quantified accurately, however, a good estimate of these limits serves the purpose of scrutinising the data for their validity. Six such limits which can be assigned for any time series are:

• Minimum value
• Lower warning level
• Upper warning level
• Maximum value
• Maximum rate of rise and
• Maximum rate of fall