28While the practice of rainwater harvesting (RWH) can be traced back millennia, the degree of its 29 modern implementation varies greatly across the world, often with systems that do not maximize 30 potential benefits. With a global focus, the pertinent practical, theoretical and social aspects of RWH 31 are reviewed in order to ascertain the state of the art. Avenues for future research are also identified. 32A major finding is that the degree of RWH systems implementation and the technology selection are

In response to water quality and quantity issues within the Stroubles Creek watershed in Blacksburg, Virginia, a retrofit bioretention cell (BRC) was installed to collect and treat runoff from an existing parking lot. The BRC was completed in July 2007, and 28 precipitation events were monitored between October 2007 and June 2008. For each storm, inflow and outflow flow-weighted composite samples were collected and analyzed for suspended sediment, total nitrogen, and total phosphorus. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were analyzed to evaluate BRC efficiency. Overall, the BRC successfully reduced flow volumes and peak flow rates leaving the parking lot by 97 and 99%, respectively. Cumulative mass reductions for sediment, total nitrogen, and total phosphorus all exceeded 99% by mass. The findings of this study have significant implications for areas with karst geology: (1) current design recommendations of lining the bottom of BRCs with clay may not be sufficient to prevent large amounts of water from infiltrating into surrounding soils; and (2) in areas with significant elevation changes, designing BRCs deeper than the typical 0.6-1.2 m increases the feasibility of retrofits and provides substantial water quality and quantity benefits.

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Rainwater harvesting (RWH) has traditionally been implemented in areas with (semi) arid climates or limited access to potable water supplies; however, recent droughts in the humid southeastern United States have led to increased implementation of RWH systems. The objectives of this study were twofold: (1) present usage characteristics and performance results for four RWH systems installed in humid North Carolina (NC) as compared with systems located in arid/semiarid regions and (2) identify system benefits and modifications that could help improve the performance of RWH systems installed in humid regions of the world. For this study four RWH systems were installed in NC. Their usage was monitored for at least one year and compared with similar studies. Results revealed that dedicated water uses and usage characteristics for RWH systems in NC differed from those previously reported in the literature. Two of the systems studied met 100 and 61% of the potable water demand with designated uses of animal kennel flushing and greenhouse irrigation, respectively. The designated uses yielding the greatest potable water replacement were often seasonal or periodic, thus necessitating the need for identifying and implementing secondary objectives for these systems, namely, stormwater management. Otherwise, the expense and effort required to implement RWH systems in humid areas will most likely preclude their use.

: In response to water quality concerns in the Jordan Lake Reservoir and state and federal mandates, several cities in North Carolina are being required for the first time to reduce nutrient loads in stormwater from previously developed lands; that is, install retrofits. It is anticipated that similar requirements will become necessary for other urban areas in North Carolina. The goal of this study is to evaluate the feasibility of alternative approaches to stormwater management for existing developments within North Carolina cities. Geographic coverage of the study included a portion of the New Hope Creek watershed, located within the City of Durham in central North Carolina. The watershed was analyzed to identify potential retrofit opportunities that could be implemented to reduce pollutant loadings entering New Hope Creek and, ultimately, Jordan Lake. Current pollutant loadings generated by the watershed, as well as reductions in annual loadings of total suspended solids, total nitrogen and total phosphorus that could be achieved by implementing the identified retrofits, were estimated. Trends and relationships between land use type and the quantity and type of retrofit opportunities were identified and conclusions were drawn as to the most appropriate types of retrofits for certain land uses.