Water Flow Regulation

Water flow regulation is defined as the ability of forested watersheds to maintain streamflows within the range best suited to the needs of the beneficiary population. This service has two main components, maintaining water above a low flow (or drought) threshold and above a high flow (or flood) threshold. Select case studies explore the ramifications of adopting a binary service metric, as well as the impacts of climate forcing on flow regulation services.
Flood regulation (a component of flow regulation) consists of the service by which forested ecosystems help maintain flow below some high flow threshold ("flood") defined by infrastructure tolerances or other social criteria.
The high flow threshold at Hubbard Brook was calculated by taking the maximum daily capacity of the Franklin Falls Dam (which drains the entire Pemigawasset River Basin), and transforming that volume of water on an areal basis. 


In the absence of social data, the high flow threshold at Turkey Lakes was set to be equal to the 95th percentile of all flows combined. This case study investigates how the use of different thresholds affects this and other flow regulation services. 

Drought mitigation (a component of flow regulation) consists of the service by which forested ecosystems help maintain streamflow below some low flow threshold ("drought") defined by water use or other social criteria.
The low flow threshold at Hubbard Brook was calculated by taking the average daily surface water withdrawals (USGS) for Grafton County, and transforming that volume on an areal basis. 


In the absence of social data, the low flow threshold at Turkey Lakes was set to be equal to the 5th percentile of all flows combined. This case study investigates how the use of different thresholds affects this and other flow regulation services. 

The "Goldilocks Zone" (GLZ) is defined as the area on the hydrograph between the high flow and low flow thresholds, or in other words, the area defined by high provision of both the flood regulation and drought mitigation services.
The percentage of time streams were maintained within the GLZ at Hubbard Brook is calculated as the percentage of days in which neither a flood nor a drought event occurred in each individual catchment. 


The percentage of time streams were maintained within the GLZ at TLW is calculated as the percentage of days in which neither a flood nor a drought event occurred in each individual catchment. 

Stability is represented by the duration (# days) between subsequent floods and droughts.
Stability of flow at Hubbard Brook was calculated as the mean duration between flood and drought events at each of the individual catchments. 


Stability of flow at TLW was calculated as the mean duration between flood and drought events at each of the individual catchments. This case study investigates how the use of different flood and drought thresholds affects this and other flow regulation services.