[en] Highlights: • Overall results show economic losses due to irrigation water in S. Fl. agriculture. • Irrigation water use penalties differ by crop and sub regions in South Florida. • Given ground water usage changes, the UEC area would experience higher penalties. • The KB area experiences a significant penalty if surface water irrigation changes. This study estimates economic loss from South Florida croplands when usage of agricultural irrigation water is altered. In South Florida, 78% of the total value of farm products sold is comprised of cropland products. The majority of Florida citrus and sugarcane are produced in the area, and agricultural irrigation was the largest sector of water use in 2010, followed by public water supply. The Florida Department of Environmental Protection announced in December 2012 that traditional sources of fresh groundwater will have difficulty meeting all of the additional demands by 2030. A shortage of water will impose significant damage to the rural and agriculture economy in Florida, which may lead to higher prices and costs for consumers to purchase citrus or other Florida agriculture products. This paper presents a methodology for estimating economic loss when usage of irrigation water is altered, and examines economic values of irrigation water use for South Florida cropland. The efficient allocation of irrigation water across South Florida cropland is also investigated in order to reduce economic cost to the South Florida agricultural sector.

[en] Highlights: • Examines past and future groundwater-induced flooding in low-lying coastal area. • Record shows water table rising with sea level, enables future flooding estimation. • Groundwater model integrates rainfall, tidal fluctuations, and sea level rise. • Model projects frequency and intensity of 2060 groundwater-induced flooding. • Sea-level-rise-bellwether area imparts science, social, and policy relevance. Modeling of groundwater levels in a portion of the low-lying coastal Arch Creek basin in northern Miami-Dade County in Southeast Florida USA, which is subject to repetitive flooding, reveals that rain-induced short-term water table rises can be viewed as a primary driver of flooding events under current conditions. Areas below 0.9 m North American Vertical Datum (NAVD) elevation are particularly vulnerable and areas below 1.5 m NAVD are vulnerable to exceptionally large rainfall events. Long-term water table rise is evident in the groundwater data, and the rate appears to be consistent with local rates of sea level rise. Linear extrapolation of long-term observed groundwater levels to 2060 suggest roughly a doubling of the number of days when groundwater levels exceed 0.9 m NAVD and a threefold increase in the number of days when levels exceed 1.5 m NAVD. Projected sea level rise of 0.61 m by 2060 together with increased rainfall lead to a model prediction of frequent groundwater-related flooding in areas < 0.9 m NAVD. However, current simulations do not consider the range of rainfall events that have led to water table elevations > 1.5 m NAVD and widespread flooding of the area in the past. Tidal fluctuations in the water table are predicted to be more pronounced within 600 m of a tidally influenced water control structure that is hydrodynamically connected to Biscayne Bay. The inland influence of tidal fluctuations appears to increase with increased sea level, but the principal driver of high groundwater levels under the 2060 scenario conditions remains groundwater recharge due to rainfall events.

[en] Highlights: • South Florida water levels may have to be increased over time to prevent the increased salt water intrusion. • Higher canal water levels also lead to an increased risk of inland flooding. • Model the relationships between flood losses and groundwater levels over time. • Analysis will help water managers better understand high water level and flood risk trade-off. High-value urban zones in coastal South Florida are considered particularly vulnerable to salt water intrusion into the groundwater-based, public water supplies caused by sea level rise (SLR) in combination with the low topography, existing high water table, and permeable karst substrate. Managers in the region closely regulate water depths in the extensive South Florida canal network to control closely coupled groundwater levels and thereby reduce the risk of saltwater intrusion into the karst aquifer. Potential SLR adaptation strategies developed by local managers suggest canal and groundwater levels may have to be increased over time to prevent the increased salt water intrusion risk to groundwater resources. However, higher canal and groundwater levels cause the loss of unsaturated zone storage and lead to an increased risk of inland flooding when the recharge from rainfall exceeds the capacity of the unsaturated zone to absorb it and the water table reaches the surface. Consequently, higher canal and groundwater levels are also associated with increased risk of economic losses, especially during the annual wet seasons. To help water managers and urban planners in this region better understand this trade-off, this study models the relationships between flood insurance claims and groundwater levels in Miami-Dade County. Via regression analyses, we relate the incurred number of monthly flood claims in 16 Miami-Dade County watersheds to monthly groundwater levels over the period from 1996 to 2010. We utilize these estimated statistical relationships to further illustrate various monthly flood loss scenarios that could plausibly result, thereby providing an economic quantification of a “too much water” trade-off. Importantly, this understanding is the first of its kind in South Florida and is exceedingly useful for regional-scale hydro-economic optimization models analyzing trade-offs associated with high water levels.

[en] Highlights: • South Florida's water management tradeoffs are examined using a hydro-economic approach • Maintaining high reliability of flows to the Everglades creates occasional urban and agricultural water shortage • System-wide tradeoffs are more pronounced under scenarios of reduced water availability • High reliability of urban water demands is possible under reduced water availability but agricultural losses are likely South Florida's water infrastructure and ecosystems are under pressure from socio-economic growth. Understanding the region's water resources management tradeoffs is essential for developing effective adaptation strategies to cope with emerging challenges such as climate change and sea level rise, which are expected to affect many other regions in the future. We describe a network-based hydro-economic optimization model of the system to investigate the tradeoffs, incorporating the economic value of water in urban and agricultural sectors and economic damages due to urban flooding while also accounting for water supply to sustain fragile ecosystems such as the Everglades and coastal estuaries. Results illustrate that maintaining high reliability of urban water supply under scenarios of reduced water availability (i.e., drier climate conditions) may trigger economic losses to the Everglades Agricultural Area, which will likely become more vulnerable as competition over scarce water resources increases. More pronounced economic losses are expected in urban and agricultural areas when flows to the Everglades are prioritized. Flow targets for coastal estuaries are occasionally exceeded under optimal flow allocations to various demand nodes, indicating that additional storage may be needed to maintain the environmental integrity of the estuarine ecosystems. Wetter climate conditions, on the other hand, generally lead to increased flows throughout the system with positive effects on meeting water demands, although flood mitigation efforts will necessitate additional releases to the estuaries. Strengths and limitations of the hydro-economic model are discussed.