Theoretical Maximum Habitat Methodology

Theoretical Maximum Habitat Scenario Habitat Methodology and Overview

Theoretical Maximum Habitat Flow Area Curves

Habitat inputs for Reorienting to Recovery theoretical maximum habitat model run are scaled versions of existing habitat to area curves from the CVPIA SIT DSMhabitat data package.

• DSMhabitat::fr_spawn$biop_itp_2018_2019

• DSMhabitat::fr_juv$biop_itp_2018_2019

• DSMhabitat::fr_fry$biop_itp_2018_2019

• DSMhabitat::fr_fp$biop_itp_2018_2019

• DSMhabitat::fr_delta$biop_itp_2018_2019

For each river in the SIT DSM, we calculated the theoretical maximum habitat for above and below dams or for unregulated rivers. See the methodology document for an in-depth overview of theoretical maximum habitat modeling methods.

Methods for Scaling the Curve

1) Calculate the flow point of reference

Inchannel Habitat: For in-channel habitat we use the flow associated with peak habitat on a given stream's flow to area curve.

Floodplain Habitat: For floodplain habitat, we use a 2-year flow value, which represents a flow that is exceeded in 50% of the years between 1980 and 2000. We calculated the 2-year, 50% exceedence value by taking the yearly rolling maximum of monthly CalSim flows and applying a cumulative distribution function on the ranked values to find the proportion of all values less than or equal to the ranked order. An interpolation function is then developed to to find the 2 year flow value.

Figure 1 - example comparison of calculated 2 year flow with the CalSim modeled monthly flow between 1980 and 2000

2) Calculate the proportion increase of habitat at flow point of reference

The proportion increase between baseline and theoretical maximum habitat was calculated using the following equation. The existing_acres were calculated using the median (for in-channel) and 2-year flows (for floodplain).

proportion_increase = (max_hab_acres - existing_acres) / existing_acres + 1

3) Scale existing habitat by proportion increase

The existing acres are then scaled for each watershed (ws) by the calculated proportion_increase.

new_hab_acres <- DSMhabitat::fr_fp$biop_itp_2018_2019[ws , , ] * proportion_increase

4) Save new data objects for Theoretical Maximum Habitat

The new data objects are saved in the package as:

• DSMhabitat::fr_spawn$r_to_r_tmh

• DSMhabitat::fr_juv$r_to_r_tmh

• DSMhabitat::fr_fry$r_to_r_tmh

• DSMhabitat::fr_fp$r_to_r_tmh

• DSMhabitat::fr_delta$r_to_r_tmh see Delta methodology for theoretical maximum habitat

Comparison plots between Baseline and Theoretical Maximum Habitat

Spawning Habitat:

In-channel Juvenile Rearing Habitat:

Floodplain Rearing Habitat:

Delta Habitat