Principle I: Active Stewardship of Our Water Resources is Essential for This and Future Generations
A. Good Policy-Making Requires Good Data
Indiana does not have one fresh water system; it has many. Northeast and northwest Indiana send water to glacial lakes and ponds and the Great Lakes. Just south of the Great Lakes Watershed boundary are the headwaters of Indiana’s big rivers. The Wabash and the White flow south and west through glacially influenced soils. These river systems characterize much of Indiana. Further south, the limestone country in south central Indiana isn’t covered by glacial till, and holds little groundwater. Water availability can be an issue in southern Indiana until, moving south, the aquifers of the Ohio River again represent an abundant water source.
Indiana’s groundwater affects its surface water (Figure 1). Stream flow during the driest periods—“base flow”—comes from two sources: groundwater aquifers discharging into the stream beds, and upstream discharges of waste water. But base flow derived from groundwater is not secure. Many sources report a consistent trend in Indiana of increases in groundwater use.
In a recent report, the GAO found that… “40 of 50 state water managers expect shortages in some portion of their states under average conditions in the next 10 years.” (Emphasis added)
General Accounting Office-14-430, May 2014
The connection between groundwater and stream flow is most visible and biologically most critical during water-constrained times, but our public policies do not fully acknowledge that relationship. The Indiana Water Shortage Plan, for example, was written to help water users in the state respond to changing conditions during droughts and declared water shortages. The plan anticipates that water users will shift from stream diversions to groundwater withdrawal (wells) during a drought. While this is practical enough, the consequences for other groundwater users and base flow to the stream during the next drought may be significant.
One impact related to increases in the use of groundwater is the effect of the combined aquifer withdrawals on the length of ephemeral and perennial streams within a basin. Many forms of aquatic life can only survive in perennial streams. In any watershed that includes a perennial stream (i.e., the stream flows all year), as one moves upstream the perennial flow diminishes until a point where the stream becomes ephemeral, that is, it only flows during the wet season. The location of this shift from perennial to ephemeral is usually a reflection of the intersection of the groundwater table with the land surface. As water levels in the aquifer change, the location of this shift from perennial to ephemeral also moves to reflect the new condition. Thus, when groundwater aquifers are depleted, the state loses perennial surface water and the aquatic life it supports.
Recommendation 1. Invest in ongoing research by the Indiana Department of Natural Resources and the United States Geological Survey designed to increase our understanding of streamflow and document the effect of groundwater upon stream flow. Add at least 65 monitoring wells to the groundwater network.
We need data to make good decisions. A direct measurement of water levels in monitoring wells in the aquifers used during shortage can determine the degree of impact and the duration of reductions in base flow to the stream as well as the reliability and the recovery rates of the aquifers themselves. However, because the state of Indiana has so few water level measurements in the aquifers around the state, it is currently not possible to determine the effect of any shifts that have occurred (or to discern the general trends in use over longer time periods) for the aquifers around the state (Figure 2). Until 2004, Indiana maintained 100 monitoring wells. Today, there are only 35. We need to re-commit to at least the hundred wells we had a decade ago, with a special focus on areas that are experiencing the most growth in use. Based on the areas with increasing groundwater use and the number of monitoring wells currently in place, we should, over the next ten years, add at least 65 new monitoring wells to the 35 now maintained. With 100 total wells, we will approach the monitoring density of our neighboring states. Figure 2 illustrates priority locations for the additional wells, based on coverage and projected demand.
As indicated above, understanding groundwater is essential for understanding low flow in streams. One of the reasons that groundwater use is a critical indicator of sustainability is that water use is more sensitive than ever before to climate shifts. In the past, Indiana farmers rarely relied on irrigation. However, in the last 20 years there has been a large increase in the use of irrigation in Indiana agriculture (Figure 3). This increase in installed irrigation pumping capacity means that a relatively small shift in drought occurrence can result in much larger shifts in water use. It is essential that we understand the implications of the increase in irrigated acres in Indiana, and that we manage the impacts to minimize loss of surface water values.
Recommendation 2. Fund the Indiana Geological Survey and others to initiate and sustain basin studies to determine the amount of groundwater and surface water availability in each watershed.
We join the Chamber of Commerce in recommending that Indiana invest in understanding stream flow. A vital first step is establishing baseline data over the next ten years on the point at which streams change from perennial to ephemeral flow.
We Are Using All of the Wabash River – and we didn’t even know it.
In 2016 a group of researchers at Purdue evaluated the water budget of the Wabash River. Their work was done to determine the sustainability of existing withdrawals in the basin given increasing diversions from the river and the aquifers in the Wabash basin. A number of databases were combined to assess how indirect reuse plays a role in meeting freshwater demands. The analysis showed that during the summer months the ratio of water withdrawal to return flow discharge back into the River is effectively 1:1. The authors argue that this is an important sustainability and yield metric of any basin.
The paper suggests that it is not possible to make informed water policy in any basin without evaluating the water budget. We need to consider what it means that during low flow months the water in the Wabash River amounts to no more than the upstream discharges. [Weiner, Jafvert, and Nies, 2016. The Assessment of Water Use and Reuse through reported Data: A U. S. Case Study, Science of the Total Environment, 539:70-77.] More generally, In order to know if water availability is being affected by use, we need reliable stream flow measurements, properly distributed groundwater monitoring wells, and an agency to organize and curate the data.