nearby waterway. The benefits of these systems include reducing pollution in streams, lakes, and nearshore coastal environments, as well as promoting groundwater recharge. The intended end use of a system will determine the level of treatment and processing of collected stormwater. Collections Stormwater collection is a process of directing water into storage from stormwater gathering, such as urban runoff. Generally, there are two types, online storages and offline storages. Online storages are a conventional way of acquiring stormwater directly from waterways or drains. For instance, the urban drainage system of channels and pipes conduct stormwater into storage facilities, often with treatment at or just prior to storage. One drawback of this collection design is the required maintenance that systems may require for structural integrity to prevent conduit failure resulting in stormwater leakage. Water Sensitive Urban Design, or WSUD , is one comprehensive planning and design process that incorporates online stormwater storage into urban development models. Offline storages require additional facilities to conduct water from waterways indirectly, and can serve as storage for stormwater prior to treatment. For instance, weirs divert flows into stormwater containment and contribute to a large part of stormwater catchment for a city, where it is then stored for future treatment and distribution. Stormwater collection is widely practiced for purposes of urban runoff and flood mitigation as well. Treatment Stormwater treatment is the greatest challenge for stormwater harvesting. Water treatment processes depend on the intended end use and the catchment equipment, which determines the level of pollutants to be filtered and removed. For instance, construction uses may only require non-potable water where the water processing includes only filtration and disinfection. However, for potable uses of higher water quality, the treatment process requires screening, coagulation, filtration, carbon adsorption, and disinfection. Storage There are three factors to consider in terms of storage: function, location, and capacity. The planner is responsible for determining the end use of the stored stormwater, such as fire fighting, industrial water supply, farming and irrigation, recreation, flood mitigation , groundwater recharge, etc. Regarding location of a system and its storage, a water tank in proximity to the waters' end use may be the best design. If the collection system is intended to slow runoff and/or recharge an aquifer, an on-site, below ground infiltration systems may be considered. Choices between online and offline storages can affect the surrounding natural aquatic systems and yields different maintenance costs