RAINWATER HARVESTING SYSTEM: SELECTION OF OPTIMAL VOLUME TANK

Abstract

The rooftop rainwater harvesting means the collection of water from the rooftop of any structure. The tank is the most expensive and critical component of  rainwater harvesting system.

The study was conducted at an individual farm in Degučiai village to find the optimum volume of the storage tank for harvested runoff from the rooftop of the farm building in years of different humidity. The precipitation data of Šilutes region over 10 years was analyzed for the water harvesting potential. In the calculations, water demand for the vegetation period is taken into consideration according to the quantities specified by the farmer.

It is determined that rainwater harvesting potential during the vegetation period is 7.53 m³ in dry years, which can meet around 24 % of the farm water needs when the catchment area is 50 m². Even in the wettest year, the farm's water demand could be satisfied only for two months. When the catchment area is 200 m²  over 7 months‘ period, it would be possible to accumulate 40.16 m³ of water  and it would fully satisfy four months‘ water demand of the farm in dry years. In wet years, all accumulated water during the vegetation period can cover all of the farm‘s water demands. Optimal volume of the tank is 11 m³ for dry and average humidity years, and up to 14 m³ in wet years, respectively.

As it can be seen from the study, the volume of the tank mainly depends on the amount of precipitation, roof area and the farm's water demand.