WHAT IS IT?      Carbon can be found in many forms in a river. Specifically, alkalinity is the amount of HCO3(bicarbonates) and CO32- (carbonates) present.

WHY IS IT IMPORTANT?      1. Alkalinity indicates the buffering capacity of a river system. Buffering capacity is the ability of a water to resisit a change in pH when an acid (H+) is added or when a base (OH-) is added. Scientists think this is done by taking acids and bases out of solution.      2. Alkalinity mitigates or relives metal toxicity by binding onto metals and taking them out of solution, making them less harmful to fish. As alkalinity increases, metals become less likely to harm aquatic organisms.

WHAT INFLUENCES IT?      1. pH: As acids or bases are added to a waterway, pH changes. Carbonates and bicarbonates buffer these changes.      2. Geology: As water flows over land, carbonates and bicarbonates in rocks and soils seep into the waterway. The longer a river flows over these rocks and soils, the more minerals the water accumulates. Aalkalinity generally increases as you move downstream.      3. Seasons: Alkalinity decreases with spring runoff during snowmelt, and increases during the winter. This is because the relative concentration of the minerals change as the volume of a river changes. With larger volumes there is usually dilution and with smaller volumes there is usually a concentration of suspended minerals.       4. Mining: Mining carries containing rocks and minerals from deep within the Earth to its surface. Once exposed, these rocks and minerals can react with rainwater and groundwater and form acidic waters which could run into local rivers and streams. pH influences alkalinity as described above.

WHAT HAPPENS AS WE TRAVEL DOWNSTREAM?

: The South Platte River as flow through downtown Denver, CO.

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