Fig. 3: Fish habitat status and trout habitat suitability with and without water markets in a future drought year.

a, Fish habitat status with no water market and improvements with mandatory cutbacks in a future drought year. Blue reaches are those with fish habitat co-benefits—improvement to intermediate ecological status in at least one month by the cutbacks. b, Fish habitat status with portfolios of water transactions that minimize the total cost to achieve reduced water consumption levels and with portfolios of environmental water transactions that minimize the total cost to achieve reduced water consumption levels and fish habitat targets of intermediate ecological status. Blue reaches are those with fish habitat co-benefits—improvement to intermediate ecological status in at least one month by the reduced water consumption-only portfolio. Green reaches illustrate how strategic portfolios substantially increase the total reach length restored to intermediate ecological status in at least one month beyond blue reaches. c, The maximum monthly improvement in trout habitat suitability from the strategic portfolio over the reduced water consumption-only portfolio. The expanded market with unprotected transactions improves the most trout habitat because 1,842 transactions are required to satisfy the reduced water consumption and fish habitat constraints, while just 118 transactions are required in the expanded market. Results for the aggressive authorized market are in Supplementary Fig. 14. Map data from Colorado’s Decision Support Systems^56,57.