Arroyo Piedras Blancas is a waterway of approximately 15 kilometers in length that flows through the region bordering the provinces of Córdoba and San Luis. The stream is noted for its clear, crystalline waters and a rocky bed, which gives it a distinct aesthetic character. It serves as a natural corridor between the two provinces, with a significant portion of its course running through the Reserva El Viejo Molino near the town of Merlo in San Luis. The area features numerous natural bathing spots and balnearios along its banks. Access for visitors is typically via a path leading from a local bar in the vicinity, though specific put-in or take-out points for formal paddling trips are not detailed. The environment faces environmental pressures, including the impact of illegal extraction of aggregates, which has altered the landscape and even eliminated some access roads along its barrancas, or bluffs. This indicates potential hazards related to unstable banks and altered water flow patterns. The stream's clarity and the presence of stones suggest a scenic, though potentially challenging, paddling environment where water levels and obstacles would be primary considerations. No specific regulations, seasonal recommendations, water temperatures, or dedicated paddler facilities are mentioned.