AZ-SF-1 Surface Runoff Flow Measurement System

Overview

The AZ-SF-1 Surface Runoff Flow Measurement System is an engineered open-channel flow monitoring solution designed for high-reliability quantification of variable-rate surface runoff under field conditions. It operates on the fundamental principle of stage-discharge relationship using calibrated hydraulic structures—specifically, a precision-machined stainless steel triangular (V-notch) weir—and non-contact ultrasonic water level sensing. The system leverages established hydrometric theory (per ISO 4359:2016 and ASTM D5490-19) wherein flow rate (Q) is derived from measured upstream water depth (H) via empirical or theoretical discharge equations (e.g., Q = C·Hⁿ). Its architecture integrates a low-turbulence flow conditioning section—a custom-length stainless steel flume—that ensures hydrostatically stable approach flow into the weir crest, minimizing velocity head errors and enabling accurate stage measurement even under partially submerged (drowned) conditions. With submergence up to 30%, measurement deviation remains below 1%; at 50% submergence, error stays within ±3%. This robustness makes the AZ-SF-1 suitable for dynamic hydrological regimes including storm-induced overland flow, snowmelt runoff, agricultural irrigation return flow, and regulated industrial effluent discharge.

Key Features

• Stainless steel (AISI 304) V-notch weir and matching flow-conditioning flume—corrosion-resistant, dimensionally stable, and compliant with ISO 4359:2016 geometric tolerances for primary flow measurement structures
• High-stability ultrasonic water level sensor with integrated temperature compensation, delivering 0.1 mm resolution and ±1% full-scale accuracy across −20 °C to +60 °C ambient range
• Industrial-grade data logger featuring 18-bit A/D conversion (±0.025% linearity), 128 MB non-volatile memory (expandable via SD card), and dual storage modes (internal + USB flash)
• Multi-interface connectivity: RS232, USB 2.0, 10/100 Mbps Ethernet, and optional GPRS module for real-time telemetry to SCADA or cloud-based platforms
• Integrated tipping-bucket rain gauge (154 mm orifice) with 0.2 mm resolution and ±1.0% volumetric accuracy—calibrated per WMO Guide to Hydrometeorological Practices (No. 168)
• Solar-rechargeable power architecture supporting continuous operation in remote off-grid locations; wide-input DC supply (10–30 VDC) with surge and reverse-polarity protection
• Programmable sampling intervals from 10 milliseconds to 24 hours; configurable output types including instantaneous value, min/max, vector average, and cumulative totalization

Sample Compatibility & Compliance

The AZ-SF-1 is validated for use in natural and engineered open channels with trapezoidal, rectangular, or V-shaped cross-sections. It accommodates flow velocities ranging from 0.05 m/s (low-flow seepage conditions) to >2.5 m/s (high-energy storm runoff), provided the approach flow is fully developed and free of air entrainment or vortices. The system meets mechanical and electrical requirements for Class II environmental monitoring per IEC 60529 (IP67 enclosure rating for sensor and junction box). All wetted components comply with NSF/ANSI Standard 61 for potable water contact. Data integrity protocols align with GLP/GMP principles: time-stamped records include sensor diagnostics, battery voltage, internal temperature, and checksum validation. Optional audit-trail logging supports FDA 21 CFR Part 11 compliance when deployed in regulated environmental reporting contexts (e.g., NPDES permit monitoring).

Software & Data Management

The AZ-SF-1 is supported by AZ-DataLink™, a Windows-based configuration and analysis suite that enables full system setup, calibration coefficient management (including user-defined H-Q curves), and real-time visualization of hydrograph trends. Raw data are stored in ASCII CSV format with ISO 8601 timestamps, facilitating direct import into MATLAB, Python (Pandas), R, or GIS platforms (ArcGIS, QGIS). The software supports automated export to FTP servers, email alerts on threshold exceedance (e.g., peak flow >5 L/s), and batch processing of multi-node deployments. Firmware updates are delivered via secure HTTPS; all communication payloads are encrypted using TLS 1.2. For enterprise integration, RESTful API endpoints allow bidirectional data exchange with third-party LIMS or water resource management systems.

Applications

• Quantification of event-based runoff coefficients in watershed-scale hydrological modeling (e.g., SWAT, HEC-HMS input calibration)
• Long-term monitoring of agricultural tile drain discharge and irrigation return flow efficiency
• Validation of green infrastructure performance (bioswales, rain gardens, permeable pavements) under simulated and natural rainfall events
• Regulatory compliance monitoring for industrial outfalls subject to EPA NPDES or EU Water Framework Directive reporting requirements
• Glacial meltwater and alpine snowmelt flux tracking in climate change impact studies
• Urban stormwater detention basin inflow/outflow balancing and detention time verification

FAQ

What hydraulic standards does the AZ-SF-1 adhere to for weir-based flow measurement?

The system follows ISO 4359:2016 (open channel flow measurement using weirs and flumes) and incorporates geometric tolerances and installation guidelines consistent with ASTM D5490-19.
Can the AZ-SF-1 operate continuously during prolonged rainfall or flooding events?

Yes—the data logger’s extended temperature range (−45 °C to +70 °C), IP67-rated sensor housing, and solar-battery hybrid power system ensure uninterrupted operation through multi-day precipitation events.
Is custom weir geometry supported for non-standard channel configurations?

Yes—AZ offers engineering consultation and fabrication of bespoke weir/flume assemblies (e.g., Palmer-Bowlus, Parshall, or custom trapezoidal profiles) with certified calibration certificates.
How is temperature drift compensated in the ultrasonic sensor?

An embedded thermistor provides real-time air temperature feedback; proprietary firmware applies NIST-traceable speed-of-sound correction to raw time-of-flight measurements.
Does the system support remote recalibration or firmware updates?

Firmware updates are performed over USB or Ethernet; calibration coefficients can be remotely modified via encrypted command protocol, with version-controlled audit logs retained in non-volatile memory.