Intensitas curah hujan yang cukup tinggi di Indonesia yang tidak dimanfaatkandengan optimal mempengaruhi keseimbangan neraca air, serta grey water yangtidak diolah kembali akan mempengaruhi kualitas badan air dan berdampak padamenurunnya kualitas lingkungan. Konsep pembangunan seperti green buildingyang menerapkan rainwater harvesting dan water recycling merupakan salahsatu usaha untuk menjaga kelestarian air. Dalam penerapan sistem tersebut,terdapat risiko yang akan mempengaruhi kinerja investasinya. Pengumpulan danpengolahan data dilakukan dengan metode survey, analisa statistik, dan montecarlo. Adapun variabel yang mempengaruhi kinerja investasinya adalah kesalahanseleksi material dan seleksi vendor, serta kesulitan prediksi produksi air olahanhujan sesuai dengan musim.

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The high intensity of rainfall in Indonesia which is not utilized optimally affect

the balance of water and grey water which is not recycled also affect the quality

of water bodies which has an impact to decrease environmental quality. The

development concept such as green building which is implementing rainwater

harvesting and water recycling is one of the efforts to preserve water. In the

application of the system, there are risks that will affect the performance of the

investment. Data was collected and processed through survey, statistical analysis,

and monte carlo. The variables which affect the performance of the investment are

a mistake of material selection and vendor selection, and the difficulty to

forecast treated rain water according to the seasons.