Dear GAMS experts,

I appeal to your kindness and goodwill to help a novice in GAMS modelling.

I’m stuggling with simple optimization problem.

I will describe the context:

Let assume that a garden needs 4277 litres of irrigation water in a day. There are three pipes that feed the garden: pipe1, pipe2 and pipe3.

Pipe1 feeds - 44% or 1882 litres

Pipe2 feeds - 31% or 1325 litres

Pipe3 feeds - 24% or 1026 litres

Each pipe is connected to several mini water collecting rezervoirs, such as:

Pipe1 has 920 rezervoirs

Pipe2 has 703 rezervoirs

Pipe3 has 317 rezervoirs

Simple calculations show the following parameters:

Pipe1 collects about 2.045 litres from each rezervoir

Pipe2 collects about 1.88 litres from each rezervoir

Pipe3 collects about 3.23 litres from each rezervoir. These can be interpreted as parameters:

Pipe1 2.045

Pipe2 1.88

Pipe3 3.23

My problem is how to model this simple example in order to optimize the number of rezervoirs by giving a total volume of water as constraint.

Let say that in a day we need 2352 litres of water in that pool or about 55%.

I’ve tried to set the exogenous variables, by setting values, positive variables, constraints but to no avail. My problem is how to construct the equations so that GAMS minimizes x number of rezervoirs per pipe using the above mentioned parameters in order to provide a volume of 2352 litres of water in total.

Many thanks in advance.