2.1.2 Temporal Design: Overview
Temporal designs describe how sampling effort is to be allocated across time. The most appropriate temporal design for you depends on your monitoring requirements,monitoring design characteristics, and monitoring constraints as identified by you in your answers to the basic questions about status and trend monitoring. When developing the temporal design of your monitoring program there are two basic units of time that you need to consider:
- Study period: The entire length of time the study will be operated. For example, the monitoring objectives of the study may include determining the long-term trend in annual abundance over 20 years so the study period would be 20 years.
- Temporal unit: The unit of time for which a metric or indicator is reported. For most long monitoring studies “year” is a temporal unit. Studies may also have more frequent temporal units that might range from seasonally to hourly. For convenience, in the following discussion, we refer to a year as the temporal unit.
Most long term monitoring objectives ask questions about patterns of change across years, sometimes decades or longer. These questions might be specific to a single location, or might cover broad regions and include many locations. The basic question we need to address for temporal designs is: what is the best allocation of sampling effort across years? Do we need to sample every site every year? Similar questions can be raised if your objectives concern a single site: does meeting your objectives require you to conduct field measurements every year (or every temporal unit if your temporal unit differs from a year)?
In some instances, categories may be combined to produce hybrid designs. For example, part of your domain might be sampled every year by the placement of facilities that count fish continuously during the relevant part of the year. The remaining portion of the domain may be best monitored by surveys that are not implemented every year.
Click here to see some examples of existing monitoring project temporal designs.