can be got by requirement per one person 
multiplying the total population. The part of 
industry use can be derived by expending quantity 
per ten thousand output value multiplying the total 
quantities of bigger user. The part of fire fighting 
and afforecast is always got from the statistics 
number per one minus. 
Forecast for development of requirement always 
needs to consider comprehensively with economy, 
population, environment , and so on. Generally , 
there are some methods like below: 
3.1.1 Method of Regression 
In the ordinary way, it appears one-variable linear 
relation between GNP and the quantity of 
requirement. Putting historical data into formula : 
Y=a+b*X 
to calculate variable a, b , then we can get the 
mathematics model of regression forecast . In the 
formula, X 1s GNP; 
Y is the quantity of requirement. 
3.1.2 Method of Expending Quantity per Output 
Value 
The formula of expending quantity per output value 
just likes: 
Q= A*B*C 
in the formula, 
A is the gross value of industrial output in 
the period of planning ; 
B is the expending quantity per output valu; 
C is the proportion in the total quantity of 
requirement; 
So, it is more important to assess rightly the three 
variables. 
3.1.3 Methods of Satistics and Analysis 
It appears certain regularity of variation among the 
continue years, and the result can be got from 
formula: 
Q=Qp*[1+p/100 ]. 
In the formula, 
Qo is the quantity of requirement in the 
datum year; 
P is varying progressively rate; 
t is the total number of statistics years. 
3.2 To Calculate the Pressure of Nodes, Flow of 
Pipes, Maintaining Current Situation 
This function can be used by government to control 
and manage the pipe net system, and also used to 
update and maintain the facilities. 
3.3 When Capacity of One Block or Some Blocks 
Change, to Calculate the Optimal Planning Pipe 
Here is the program of establishment of refining 
water pipe net system ( figure 1.). 
3.3.1 Data Preparation 
This procedure is used to edit and arrange data, and 
to supply basic data for next procedure. It includes 
mainly some aspects: 
* To input water pipe map to computer, edit 
them, and create topology relation of pipes. 
* To add information such as diameter and 
flow of pipes to Arc Attribute Table (AAT), 
and elevation of nodes to Node Attribute Table 
(NAT); 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996