Try elimination communication, it will reduce the number of nappies used.
Front loaders use much less water than top loaders.
Prioritise, if there is simply not enough water to be able to justify using cloth nappies at certain stages, don’t use them, or use them part of the time. An alternative is using home compostable disposable nappies instead (eg Eenee disposables)
Routine with strict water restrictions
Thorough hand wash with detergent, with saved bath or shower water.
Dilute bleach soak.
Through hand rinse or machine rinse.
This routine may result in greater wear on modern cloth nappies, it is better suited to flats.