From IMS Consulting Group:
A simple but efficient app to monitor river flows, gage heights and water temperatures at USGS stream gage sites in Montana, Wyoming, Colorado, Idaho, Utah, New Mexico, Washington, Oregon and California. (Note: Not all sites report gage height and/or temperature, and some sites only report seasonally). An invaluable tool for fly fisherman, canoeists, kayakers, river recreationists, hydrologists and civil engineers. Monitor up to 24 rivers or streams, and set alerts to closely monitor changes.