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Conceptual Model Approach

What is a Model

Model airplanes, Ansel Adam's photographs, paper mache volcanoes. These are all models.

Scientific models represent patterns found in nature. Mathematical ones use numbers or complex formulas to describe a system in a way that can be "plugged into" a computer to run various scenarios.

Conceptual models use diagrams, narratives and/or tables to represent a set of causal relationships. The Delta Conceptual Models are conceptual models, using a Driver-Linkage-Outcome (DLO) approach, as described below.
Diagram illustrating conceptual model approach.

This diagram shows an example of the DLO framework. An increase in nutrient levels leads to an outcome of increased growth and establishment of submerged aquatic vegetation (SAV).

See the Current DRERIP Delta Conceptual Models

The Driver-Linkage-Outcome (DLO) Approach

The DRERIP conceptual models employ a cause and effect method (deterministic paradigm), using the DLO approach: drivers (D), linkages (L), and outcomes (O):

  • Drivers are physical, chemical, or biological forces that control the species or system of interest.
  • Linkages are cause-and-effect relationships between drivers and outcomes.
  • Outcomes are response variables (such as reproductive success, growth, and mortality) that the conceptual model is attempting to explain. In the context of the DRERIP species conceptual models, "ultimate" outcomes reflect population or system-level responses to drivers.

The path between an environmental driver (e.g., temperature regime in a specific sub area) and an "ultimate" outcome (e.g., reproductive performance, plant growth) may pass through one or more "intermediate outcomes". These outcomes then serve as a "driver" for the next outcome in the series.

Peer Review

Scientific peer review is an essential component of the DRERIP process to maintain scientific integrity and allow for science-based adaptive management. Both the conceptual models and the scientific evaluation underwent peer review. See a detailed explanation of the peer review process. (PDF)