Flood and recharge relationships of the lower Rio Puerco, New Mexico
— D. L. Heath

The Rio Puerco, largest of the New Mexico tributaries to the Rio Grande, drains a watershed area of 7,350 mi² (19,040 km²) in the northwest quadrant of the state (fig. 1). This region includes parts of the Colorado Plateau, Basin and Range, and Southern Rocky Mountain physiographic provinces. From its source 10,500 ft (3200 m) above sea level in Sandoval County, the Rio Puerco flows southward for about 170 river miles (274 km) through a varied landscape of steep canyons, narrow alluvial valleys and sloping mesas to join the Rio Grande near the community of Bernardo.

The gradient of the Rio Puerco is about 78 ft/mi (14.8 m/km) in the reach above the confluence with Arroyo Chico, 13 ft/mi (2.5 m/km) to the confluence with the Rio San Jose and about 8 ft/mi (1.5 m/km) to its mouth at the Rio Grande. Annual precipitation in its basin ranges from an average of 7 in. (180 mm) in the lower elevations to over 17 in. (430 mm) in the mountainous areas. Much of the rainfall, which occurs as a result of convective thunderstorms from July through October, produces rapid runoff, flash flooding and severe erosion. The river is notorious for its high concentrations of suspended sediment, and is a major contributor to sediment deposition in the middle Rio Grande valley from San Acacia to Elephant Butte Reservoir, 80 mi (129 km) from its mouth.

The Rio Puerco is a losing stream; that is, it loses water through its bed. The records of surface-water flow from 1940 to 1976 at the Rio Puerco and Bernardo gaging stations show that an average of about 1.7 x 106 ft³/mi/yr (30,000 m³/km/yr) is lost by infiltration in the 48 mi (78 km) of channel between these two stations. Flood and recharge relationships in an alluvial river system, such as the Rio Puerco, depend upon many factors, including geology and geomorphology, peak discharge, flow duration, climate, vegetation, and the occurrence and movement of groundwater in underlying sediments. Some results of a study that concentrated on the area of the lower Rio Puerco, extending from the mouth of the Rio San Jose southward to the confluence of the Rio Puerco and the Rio Grande at Bernardo, New Mexico, are presented in this paper.