1.   Purpose and objectives

     To compute and analyse statistics of low flows and hence to estimate the probability of low flows into reservoirs.

2.   Description
        
     LOWSTATS is a suite of three computer programs which was developed originally to provide probability based estimates of future inflows to major reservoirs in the State of Victoria, Australia. The programs however, have potential for wider application. Their functionality includes:

     * The computation of daily and monthly natural inflows into a  
       storage (using a water balance method and an analogue method which 
       utilises gauged information within the catchment);
     * unconditional low flow frequency analysis of monthly streamflow 
       data (which involves fitting a family of curves to monthly flow 
       data which expresses the relationship between flow magnitude and 
       probability for different durations of total flow); 
     * low flow frequency analysis of monthly streamflow data, conditional 
       upon antecedent conditions (which involves determining the 
       conditional probability distribution, given antecedent conditions, 
       of flows for a given duration and ending month).

     The programs are user-friendly and robust, but should only be used by someone with the appropriate background and experience in the hydrological concepts involved. A User Manual is provided but it only describes the operation and use of the software; it is not a didactic text for the 
benefit of those without hydrological experience.

3.   Input

     * Daily streamflow, rainfall, evaporation, reservoir level data 
       files, rating curve data for reservoirs, estimated groundwater 
       inputs to reservoirs, pan factors, runoff coefficient.
     * Monthly streamflow data file, durations to be analysed.
     * Monthly streamflow data file, duration to be analysed and 
       antecedent period.

4.   Output

     * Daily and monthly inflows to reservoirs.
     * Quantile estimates for exceedance probabilites of 99.5%, 99%, 98%, 
       95%, 90%, 80%, 70%....10% (in tabular and graphical form); 
       historical statistics of the minimum, mean and maximum flows for 
       the given duration and the years in which these occurred.
     * Quantile estimates for exceedance probabilities of 99.5%, 99%, 98%, 
       95%, 90%, 80%, 70%....10% (in tabular and graphical form).

5.   Operational requirements and restrictions

     The system hardware requirements for operation of the software are as follows:

     * an 80386-, 80486- or Pentium-based IBM compatible personal 
       computer;
     * an Intel or compatible math coprocessor;
     * PC-DOS or MS-DOS Version 3.3 (or Compaq DOS 3.31) or higher; a VGA 
       or SVGA monitor.

6.   Form of presentation
        
     IBM compatible PC-based computer program on disc with User Manual.

7.   Operational experience

     Program has been used within Australia, primarily by the Department of Natural Resources & Environment and major water authorities in the State of Victoria.

8.   Originator and technical support

     The program was developed by Mr B. James & Mr E. Weinmann of the former Rural Water Corporation of Victoria and adapted for operation on a DOS operating system by Mr R. Nathan (now of Sinclair Knight Merz) for the Water Bureau, Department of Natural Resources and Environment, Victoria. Questions about the program should be directed to the Water Bureau.

9.   Availability

     From the HOMS National Reference Centre for Australia.

     The program is only available to government departments/agencies and water authorities and educational institutions and must not be used for commercial gain.

10.  Conditions on use

     Users of the program are required to complete, sign and return to the Water Bureau, a "Terms and Conditions of Supply" form acknowledging that:

     * the performance of the LOWSTATS software is not guaranteed;
     * the Department of Natural Resources & Environment and Sinclair 
       Knight Merz are not liable for any damage arising from the use  or 
       abuse of LOWSTATS software;
     * the software and associated documentation may be copied and used 
       only by the organization completing the form.