Court challenges to the use of tiered water rates in California are threatening the state’s own water conservation and affordability goals. That’s what’s at stake in a case called Patz v. City of San Diego.   Climate change is intensifying California’s hydrologic variability and exacerbating the state’s water supply challenges. Dwindling water supplies have led to a substantial increase in the retail cost of water over the last decade. Drought-induced water shortages force water agencies to invest in additional supplies or enact expensive emergency measures. These costs are often passed on to households through increased rates and surcharges and fall disproportionately on low-income Californians, many of whom have seen their incomes stagnate.