Methods, systems, and techniques for detecting at least one of an influx event and a loss event during well drilling involve using one or both of errors between 1) estimated and measured pit volume, and 2) estimated and measured flow out, to identify or determine whether the influx or loss event is occurring, or to sound some other type of related alert. These determinations may be performed in a computationally efficient manner, such as by using one or both of a time and depth sensitive regression.