Opinion ID: 1253871
Heading Depth: 3
Heading Rank: 1

Heading: Arizona's Bifurcated System of Water Rights

Text: ¶ 7 In Gila River II, we summarized the bifurcation of Arizona law respecting surface water and groundwater: [R]ights associated with water found in lakes, ponds, and flowing streamssurface waterhave been governed by the doctrine of prior appropriation.... On the other hand, underground water has been governed by the traditional common law notion that water percolating generally through the soil belongs to the overlying landowner, as limited by the doctrine of reasonable use. [3] 175 Ariz. at 386, 857 P.2d at 1240. ¶ 8 Arizona does not entirely confine the doctrine of prior appropriation to surface waters. Our courts have extended prior appropriation to a category known as subflow, historically defined as those waters which slowly find their way through the sand and gravel constituting the bed of the stream, or the lands under or immediately adjacent to the stream, and are themselves a part of the surface stream. Id. at 387, 857 P.2d at 1241 ( quoting Maricopa County Mun. Water Conserv. Dist. No. 1 v. Southwest Cotton Co., 39 Ariz. 65, 96, 4 P.2d 369, 380 (1931) ( Southwest Cotton )). The notion of subflow is significant in Arizona law, for it serves to mark a zone where water pumped from a well so appreciably diminishes the surface flow of a stream that it should be governed by the same law that governs the stream. Id. at 96-97, 4 P.2d at 380-81. ¶ 9 Yet the notion of subflow is an artifice, as we acknowledged in Gila River II, that rests on a hydrological misconception. 175 Ariz. at 389, 857 P.2d at 1243. To pump well water from lands under or immediately adjacent to a stream is not, we now know, the only pumping that may significantly diminish surface flow. The hydrological connection of groundwater and surface water is sometimes such that groundwater pumped more distantly within an aquifer may have comparable effect. Leshy and Belanger [4] explain: When water is pumped from an aquifer by means of a well, it creates what is known as a cone of depression. This is caused by the groundwater in the aquifer moving toward the well. If the material in the aquifer has a high transmissivity value, the cone of depression will be wide and shallow. If, on the other hand, the aquifer does not easily transmit water, the cone of depression will be steep and narrow. If water is pumped continuously from the well, the cone of depression will become larger. If the water table is close enough to the earth's surface to allow this cone to cut into a surface stream, water from the stream would directly infiltrate into the ground, following the slope of the cone of depression until it reached the well. Even if the cone did not intersect the stream directly, it could affect the amount of water in the stream by intercepting water that would otherwise migrate toward the stream. This would cause less water to be available in the stream bed. If water were removed by pumping from a well and none were reintroduced, the water table would decline. If several wells were pumping, there would be a more rapid decline. Any time the rate of water withdrawn from an aquifer exceeds the rate of recharge, the water table will decline. Leshy & Belanger, 20 Ariz. St. L.J. at 663-64. ¶ 10 Conforming their law to hydrological reality, most prior appropriation jurisdictions by now have abandoned the bifurcated treatment of ground and surface waters and undertaken unitary management of water supplies. Id. at 659-60. In Gila River II, however, we declined to do so, explaining: [I]t is too late to change or overrule [ Southwest Cotton ].... More than six decades have passed since Southwest Cotton was decided. The Arizona legislature has erected statutory frameworks for regulating surface water and groundwater based on Southwest Cotton. Arizona's agricultural, industrial, mining, and urban interests have accommodated themselves to those frameworks. Southwest Cotton has been part of the constant backdrop for vast investments, the founding and growth of towns and cities, and the lives of our people. Gila River II, 175 Ariz. at 389, 857 P.2d at 1243. Limiting ourselves to interpreting Southwest Cotton, not refining, revising, correcting, or improving it, we reaffirm[ed] Southwest Cotton's narrow concept of subflow and directed the trial court to devise a subflow standard on remand that turns on whether the well is pumping water that is more closely associated with the stream than with the surrounding alluvium. Id. at 389-93, 857 P.2d at 1243-47.