Iowa Lakes Valuation Project



A simple organism that that produces chlorophyll through photosynthesis.

An overabundance of these organisms (so-called algal blooms) may discolor the water and use up available nutrients.


A green pigment produced by green plants including algae that is essential to photosynthesis, or the conversion of light, carbon dioxide, and water to oxygen. Chlorophyll concentration is often used as an approximate index of algal biomass. Measured in µg/L or ppb.


Photosynthesizing, single-celled organisms that live mostly in fresh water, sometimes referred to as blue-green algae but they are classified as bacteria. In overabundance, they can use up oxygen and block sunlight in a body of water.

Ecosystem services

A term used to describe a wide variety of services that ecosystems and the environment as a whole provide to people.


A nutrient-rich lake. It tends to be shallow, "green," and has limited oxygen.

Expenditures Impact

Spending in total dollars generated locally by an environmental improvement and/or the number of local jobs these expenditures generate.

Maximum willingness to pay (MWTP)

An economic value measure, the MWTP is the amount an individual is willing to pay for a good or service and, in so doing, forgo other goods and services that are available for purchase.


A lake with nutrients that fall between eutrophic and oligotrophic levels, or mid-level nutrient concentration.

Nonpoint source pollution

Unlike pollution that can be traced to a single point or points, such as an industrial waste spill, nonpoint source pollution comes from many diffuse sources. Nonpoint pollution is picked up as water moves over or through soil and is finally deposited in lakes, rivers, coastal waters, or even watersheds. Pollutants can include pesticides, herbicides, and fertilizers from agricultural lands and nutrients from livestock operations.


A lake that is nutrient poor, usually clear and deep, with high concentrations of dissolved oxygen.


A chemical element and nutrient important in water quality measures. Its quantity controls the extent of algal growth in a lake. Too much phosphorus in a lake causes more algae to grow, which in turn reduces the amount of light that can penetrate the water and reduces oxygen.


Parts per billion.

Secchi disk

A flat, black and white disc that used to measure the transparency of water. The disk is lowered into water by a rope until a pattern on the disk is no longer visible.

Secchi depth

The depth at which the Secchi disk disappears from sight when lowered into a body of water.