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AbstractRainfed agriculture in Prince Edward Island is affected by climatic changes like warming, seasonal shifts, varying precipitations, and reducing water availabilities, all questioning its sustainability. Projecting future scenarios was critically important; therefore, spatiotemporal variations in potential evapotranspiration (PET), crop water requirements (CWRs), effective rainfall (ER), supplemental irrigation requirements (SIR), and sustainable water availabilities (SWAs) were analyzed. Average annual PET was predicted to insignificantly increase (3% to 6%) under RCP4.5 during the next 30–60 years, with two to four times increase in colder months (January–April) and a significant reduction during August–December. Accordingly, historical CWR of potatoes (currently ~425 mm) would decrease by 5% to 9%, except for the least likely RCP8.5 scenario, which projects ~10% increase in 2051–2080. That, and changes in ER, would cause SIR to decrease to 50–90 mm in normal years, but two to three times higher during dry years, and almost no SIR in wet years. Spatially, SIR increases by ~40 mm from east to west and is expected to be higher in 2021–2050 than 2051–2080. Monthly SIR ranges in normal years would be July: 02–36 mm, August: 31–48 mm, and September 04–20 mm. Existing water policy allows pumping up to 20% of yearly recharges (annual SWA) and up to 35% of summer's streams baseflows (summer SWA). Despite insignificant reductions in annual SWA (3% to 17%) for the next 30–60 years, summer SWA may be reduced 38% to 50% due to temporal redistribution. Even in dry years, the reduced amounts would still be sufficient to fulfill SIR in the eastern forest‐dominated Bear River watershed and SIR in normal years in the central zone; however, they would not be enough to enable the entire cultivated area of western zone. In normal years, SIR would consume: 5% to 6%, 27% to 37%, and 63% to 79% of annual SWA in the eastern, central, and western zones, respectively. Sprinkler irrigation to meet SIR is challenging, more economic evaluations and policy adaptations are needed for sustainable agricultural management.

AbstractPrince Edward Island (PEI), Canada, entirely depends on groundwater for freshwater supplies, which also highly feeds streamflows. In a few watersheds, pumping has had disturbed steady‐state conditions and reduced streamflows. Spatiotemporal hydrological analysis of streamflows and recharges was performed in its scattered watersheds. Mill, Wilmot, West, Winter, and Bear River watersheds were modeled by the Soil and Water Assessment Tool (SWAT) under the shallow water‐table conditions, besides other analyses. The model was calibrated against 120 observed mean monthly flows (1995–2004) and validated for another 120 observations (2005–2014), with Nash–Sutcliffe efficiency (NSE) as the major performance assessment parameter. The model accurately simulated mean monthly flows for all watersheds during 1995–2014, except Winter River watershed (NSE = 0.02–0.33), wherein it overpredicted by 31%–52% and 5–12% in Wilmot River (NSE = 0.28–0.64). Streamflows were found highly dependent on groundwater; therefore, pumpings of 6.92 and 0.73 million cubic meters (MCM)/year caused the overpredictions in Winter and Wilmot watersheds, as SWAT cannot account pumping. In the rest three watersheds with negligible pumping, 4%–18% underprediction was due to multisite calibration. Spatially, streamflows randomly varied between 555 and 811 mm/year across watersheds, whereas thick and highly permeable sandstone produced higher recharges, the maximum ~600 mm/year in the eastern forest‐dominated Bear River watershed, lesser in western ~330 mm/year, and moderate ~450 mm/year in central watersheds. Temporally, March–May are the months of highest streamflows, whereas recharge is maximum during April–July. The succession trend justified strong surface water–groundwater interactions. Existing Water Extraction Permitting Policy ensures sustainability at the island scale. It sets pumping limit at 20% of recharge, that is, 0.48 km3/year altogether, against the present pumping of ~0.04 km3/year, yet a few watersheds are somewhat water‐stressed due to population and pumping concentration. Expansion of streamflow and groundwater monitoring, promoting population and pumping in rural areas, and more scrutiny for further pumping permits in water‐stressed watersheds are quite important for sustainable water management in PEI.

AbstractTo understand climate change impacts on Prince Edward Island (PEI), Canada, historical daily precipitation and temperature of the island was investigated between the periods: 1931–60 (1940s), 1961–90 (1970s), and 1991–2020 (2000s) in its eastern, central, and western parts. Observed climatic data were utilized, augmented by some validated modeled data of Pacific Climate Impact Consortium (PCIC) for missing years. Statistically significant warming of the island was found ranging from 1.14°C in the east to 0.75°C in the west from the 1970s to 2000s. The warming trend during the period was distributed throughout the year including winters. In the east, mean monthly temperature significantly increased in all the months except for January, March, and June. Significant increase in temperature was found solely during August (+0.80°C) in central, and for August (+0.64°C), September (+0.99°C), and October (+0.73°C) in western parts. Proportionate increase in annual minimum temperature was greater than the maximum, particularly in eastern (+1.57°C) and central (+0.75°C) parts and thus indicated moderated cold there. Over the same 30‐year period, annual precipitation increased 6 percent in the east but decreased 5 and 8 percent in the central and the western PEI, respectively. The changes in precipitation were not statistically significant, except snowfall reduction (−20%) in the west, which was a statistically significant change. Interannual precipitation variations during wet and dry years having 20 and 80 percent probabilities of exceedance, respectively, ranged 350–470 mm/year during 1991–2020. Rainfall intensities, measured by hourly data, increased from 1.15 to 2.24 mm/hr, on average in central and western parts, respectively, in 2004–17 compared to 1970s. Impacts of the rising temperatures, decreasing precipitation, and uneven and intense rainfalls patterns on water resources and rainfed agriculture need further investigations. Climate change adaptations be included in existing water policies to mitigate the impacts.