Found motivation to look it up. This document suggests leaving enough space between the rows to accomodate the runoff. "EMLR allows solar panels associated wit

Found motivation to look it up. This document suggests leaving enough space between the rows to accomodate the runoff. "EMLR allows solar panels associated with ground-mounted solar farms to be considered pervious if they are configured in accordance with the recommendations in this chapter. These recommendations promote sheet flow of stormwater from the panels and natural infiltration of stormwater into the ground beneath the panels." ... "In general, the minimum disconnection length between two rows of solar panels is equal to the width of each row, as shown in Figure 1. However, some panel layouts include horizontal gaps between individual modules that allow stormwater to drip off the panels at intervals much smaller than the width of each row. In these instances, the solar farm can be designed with a smaller disconnection length, provided that they will not cause concentration of stormwater runoff." https://deq.nc.gov/media/12043/download https://deq.nc.gov/media/12043/download