Table 1.
Summary of previous studies and refinement to current study.
Fig 1.
Workflow of sustainability assessment of basin-wide agricultural systems in the Albemarle-Pamlico.
The middle three components (solid boxes) are supported with corresponding dotted boxes, culminating in a basin-wide sustainability indicator evaluation.
Fig 2.
Agricultural RWH system for irrigation to major crops in areas greater than 10% of total farm within the Albemarle-Pamlico basin (Figure modified from Ghimire and Johnston [55]; ARWH = agricultural RWH).
Fig 3.
(a) Crop areas and (b) estimated annual supplemental irrigation water needs for the crops (>10% area coverage) with ±50% variation in demands in this study.
“All others” include but are not limited to tobacco, peanuts, sorghum, potatoes, millet, oats, rye, barley, triticale, and fruits and vegetables such as cucumbers, watermelons, peppers, etc. Note: Quinoa is currently not cultivated in the region; however, we assumed the area equivalent to wheat’s area.
Table 2.
Description of Cluster 1 decision management objectives (DMOs).
Note: baseline system consisted of RWH components: 13000 m3 sediment chamber, 155 m 101.6 mm diameter collection and distribution polyvinyl chloride (PVC) pipe, a polyethylene (PE) water holding tank, a pump, pumping energy, a pivot-center, control valves, and check valves, designed for corn crop irrigation adopted from Ghimire et al. (2014). All DMOs were a modification of the baseline system.
Table 3.
Description of Cluster 2 decision management objectives (DMOs).
Table 4.
A summary of cropland, supplemental water needs, and RWH systems in the research site.
Sc = αSrc where, α = the ratio of crop water need to reference crop water need, Sc = supplemental irrigation water need; Src = the supplemental irrigation water need for the reference crop, corn (211.3 mm), obtained from Ghimire and Johnston [54]: HIGH = Highlands; PIED = Piedmont; COAS = Coastal; N/A = not available. Note: the number of agricultural RWH systems irrigating a specified crop, i, was calculated as the ratio of actual total crop area to average unit farm area (343,983 m2, obtained from Ghimire and Johnston [54]. Although quinoa is currently not cultivated in the region, analyses were conducted equivalent to wheat’s area.
Fig 4.
(a) Group 1- mean normalized life cycle impact assessment and life cycle cost assessment values (dimensionless) of 16 decision management objectives (DMOs) for agricultural RWH systems irrigating four major crops resembling current practices in the southeastern U.S. (b) Group 1- Sustainability scores of 16 DMOs.
Note: DMO1 = baseline system pasture-grass irrigation; DMO2 = baseline system cotton irrigation; DMO3 = baseline system corn irrigation; DMO4 = baseline system soybeans irrigation; DMO5 = concrete tank system pasture-grass irrigation; DMO6 = concrete tank system cotton irrigation; DMO7 = concrete tank system corn irrigation; DMO8 = concrete tank system soybeans irrigation; DMO9 = no pump system PE tank pasture-grass irrigation; DMO10 = no pump system PE tank cotton irrigation; DMO11 = no pump system PE tank corn irrigation; DMO12 = no pump system PE tank soybeans irrigation; DMO13 = no pump system concrete tank pasture-grass irrigation; DMO14 = no pump system concrete tank cotton irrigation; DMO15 = no pump system concrete tank corn irrigation; and DMO16 = no pump system with concrete tank soybeans irrigation.
Fig 5.
(a) Group 2- mean normalized life cycle impact assessment and life cycle cost assessment values (dimensionless) of 24 decision management objectives (DMOs) for combined systems of optimal agricultural rainwater harvesting (RWH) irrigating four representative crops (b) Group 2- Sustainability scores of 24 decision management objectives (DMOs).
Note: DMO1 = 0%RWH-Corn; DMO2 = 0%RWH-Soybeans; DMO3 = 0%RWH-Wheat; DMO4 = 0%RWH-Quinoa; DMO5 = 20%RWH-Corn; DMO6 = 20%RWH-Soybeans; DMO7 = 20%RWH-Wheat; DMO8 = 20%RWH-Quinoa; DMO9 = 40%RWH-Corn; DMO10 = 40%RWH-Soybeans; DMO11 = 40%RWH-Wheat; DMO12 = 40%RWH-Quinoa; DMO13 = 60%RWH-Corn; DMO14 = 60%RWH-Soybeans; DMO15 = 60%RWH-Wheat; DMO16 = 60%RWH-Quinoa; DMO17 = 80%RWH-Corn; DMO18 = 80%RWH-Soybeans; DMO19 = 80%RWH-Wheat; DMO20 = 80%RWH-Quinoa; DMO21 = 100%RWH-Corn; DMO22 = 100%RWH-Soybeans; DMO23 = 100%RWH-Wheat; DMO24 = 100%RWH-Quinoa.
Fig 6.
Sensitivity of sustainability indicators of combined systems (combined optimal agricultural RWH and well-water system) to the fraction of well-water; vertical arrow indicates an example threshold 40%; the % may be adjusted lower or higher.
Note: The LCIA and LCCA values for each category were normalized with respect to maximum value.
Fig 7.
Sustainability indicators of agricultural systems of four RWH design configurations to irrigate the basin’s four major crops basin wide at a 25% adoption rate; results correspond to the most sustainable DMOs for each crop type with the variation in supplemental water demands of ±50% as depicted by horizontal bars.
Unit prefixes are P = Peta; M = Mega; t = Metric ton; k = kilo; G = Giga; and CTU = comparative toxic units.
Fig 8.
Sustainability indicators of agricultural systems of combined RWH and well-water systems at 0.4 well-water:0.6RWH to irrigate the four globally representative crops at a 25% adoption rate basin wide; results correspond to the most sustainable DMOs for each crop type with the variation in supplemental water demands of ±50% as depicted by horizontal bars.
Unit prefixes are P = Peta; M = Mega; t = Metric ton; k = kilo; G = Giga; and CTU = comparative toxic units.
Fig 9.
Sensitivity of sustainability indicators of combined systems (combined RWH and well-water systems) to crop irrigation water needs at a 25% adoption rate basin wide.
Percentages (%) were computed with respect to original irrigation water needs of crops.