Simple Tool for Analyzing Canal Systems in Mixed Urban and Rural Environments

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

SIMPLE TOOL FOR ANALYZING CANAL SYSTEMS IN MIXED URBAN AND RURAL ENVIRONMENTS

Brian Wahlin1, Bert Clemmens2, Brent Travis3 and Jorge Garcia4

ABSTRACT

In many locations throughout the world, urbanization is encroaching on rural areas. In the United States, this encroachment typically leads to conversion of open channel irrigation ditches into underground pipes. Years of urbanization from a wide variety of land developers can convert an open channel system to a patchwork system that changes from open channels to a piped system and back again several times along the length of the canal. This constant change of the physical conditions of the irrigation system makes determining the capacity of the overall system challenging. As an example, the Salt River Project (SRP), an irrigation water provider in Phoenix, Arizona, USA, has a partnership with the City of Goodyear, Arizona, USA, that allows the City of Goodyear to utilize SRP’s infrastructure to deliver water to a water treatment plant if there is sufficient capacity in SRP’s system to carry that additional water. However, SRP’s lateral system was composed of a number of open channel and piped sections, making it difficult to know the current capacity. To determine the capacity in these complicated systems, a simple spreadsheet tool was developed that includes automatic calculation of backwater between structures. Using this tool, the hydraulics for combination of piped and open channel systems can be easily determined using this spreadsheet tool.

Keywords : Urbanization, Infrastructure, Open Channels, Pipelines

1. INTRODUCTION

1.1 The Salt River Project

The Salt River begins in eastern Arizona near Springerville and winds its way west through the Phoenix area. Along the way, the Salt River is joined by the Verde River, which begins near Seligman and flows south. These two rivers create a watershed area of over 33,600 km2 (13,000 mi2) as shown in Figure 1. The flow of the Salt and Verde Rivers through the Phoenix area has allowed this area to be settled and grow. The Salt River Project (SRP) has been instrumental in stabilizing the water supply for the Phoenix metropolitan area. The SRP system consists of four dams on the Salt River and two dams on the Verde River.

SRP provides electricity to retail customers in the Phoenix area and operates or participates in seven major power plants and numerous other generating stations. SRP also delivers nearly 1.2 billion cubic meters (1 million acre-feet) of water to their 970 km2 (240,000 acre) service area. The water delivery area for SRP is approximately 15% agriculture and 85% urban. SRP maintains and operates an

1 Vice President, WEST Consultants, Inc.; 8950 S 52nd Street, Suite 210, Tempe, AZ, 85284; E-mail: [email protected] 2 Senior Hydraulic Engineer, WEST Consultants, Inc.; 8950 S 52nd Street, Suite 210, Tempe, AZ, 85284; E-mail: [email protected] 3 Director of Applied Research, WEST Consultants, Inc.; 8950 S 52nd Street, Suite 210, Tempe, AZ, 85284; E-mail: [email protected] 4 Engineer Principal, Salt River Project; Mail Station SSW303, P.O. Box 52025, Phoenix, AZ 85072; E-mail: [email protected]

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32 extensive water deliver system, which includes dams, reservoirs, wells, canals, laterals, and pipelines.

Figure 1. Location figure for the Salt River Project watershed and service area (SRP, 2002).

1.2 Salt River Project Lateral System

The SRP lateral canals consist of open channel canal or pipeline sections divided by check structures. While most of the system was originally open channel canals, a large portion of SRP’s lateral system has been converted to pipelines as development took place. When a canal was converted into a pipeline, the check structure was replaced with a head box (see Figure 6). These head boxes perform the same function as check structures do in an open channel system. On the upstream side, the pipeline enters the head box. The head box includes a weir wall with a gate below the weir. If the gate is closed, the water rises in the head box until it spills over the weir. These weirs are operated by the zanjero to control water levels for delivery gates. On the downstream side, the pipeline exits to head box and continuesalong the pipeline downstream. If water is not delivered to turnout structures from a head box, sometimes the head box is no longer used to control water surface elevation, and therefore is considered abandoned. Manholes are installed at regular locations along the pipelines. These manholes cause head losses in the pipeline system.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

2. PROBLEM DESCRIPTION

The City of Goodyear, Arizona, USA, has seen a population explosion in recent years (see Figure 2). The State of Arizona requires that a 100-year water supply be secured prior to any new development. As such, the City of Goodyear is looking for ways to increase their secured water supply. Currently, the City of Goodyear is in the process of designing a new water treatment plant to meet the needs of the expanding population. However, for geographical reasons, it is difficult to get water to this proposed facility. One possible option is for the City of Goodyear to utilize SRP’s lateral system to bring water from the Grand Canal, one of SRP’s main water delivery canals, to the City’s planned water treatment plant. Water routed through SRP’s lateral system would be delivered to the Buckeye Feeder Canal and the City of Goodyear would withdraw water from the Buckeye Feeder Canal.

Figure 2. City of Goodyear is located west of Phoenix, Arizona.

SRP is willing to allow the City of Goodyear to utilize the excess capacity in their lateral system. However, SRP does not want to have any interruption in their deliveries to their clients. In addition, if there are any bottle necks in the lateral system that would require capital improvements in order to successfully carry the excess water for the City of Goodyear, then SRP desires that the City of Goodyear pay for those capital improvements.

The area identified to possibly deliver water to the Buckeye Feeder Canal includes the lateral canals off of SRP’s Grand Canal from 35thAvenue to roughly 115thAvenue in Phoenix, Arizona. In SRP’s system, the Grand Canal is designated as “Canal 2”. Laterals are designated by the number of mile downstream from the main canal. Thus, Lateral 2-23 is a lateral off the Grand Canal (i.e., Canal 2) that is roughly 23 miles (37 km) downstream from the canal heading. The area that could potential be used to deliver water to the City of Goodyear includes lateral canals and pipelines from 2-15 to 2-23 plus drains that supply the Buckeye Feeder Canal at roughly 115thAvenue and Broadway Road in Phoenix, which covers Service Area 26 ( Figure 5) and Service Area 24 (Figure 4).Laid end to end, the lateral system in this area is approximately 193 km (120 miles) long, frequently switching between open channels and closed pipelines. As-built drawings exist for many of the laterals, pipelines, and head boxes, but these plans were frequently difficult to read. In addition, some areas in which improvements had been made had no drawings and some areas had missing drawings. A typical lateral is shown in Figure 3.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

Figure 3. Lateral 2-23 along 115thAvenue south of Lower Buckeye Road.

Before formalizing an agreement with the City of Goodyear, SRP needs to understand the existing capacity and capacity restrictions of their lateral system in this area. However, since their lateral system has morphed into a patchwork of interconnected open channels and pipelines with a large amount of data that may or may not be correct, estimating the existing capacity and identifying capacity restrictions is problematic.

To determine the capacity in these complicated systems, WEST Consultants, Inc. (WEST) developed a simple spreadsheet tool that includes automatic calculation of backwater between structures. Using this tool, the hydraulics for combination of piped and open channel systems can be easily determined using this spreadsheet tool.

Figure 4. SRP Service Area 24.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

Figure 5. SRP Service Area 26.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

3. SRP REQUIREMENTS

SRP irrigation laterals consist of a series of canal or pipeline segments that are interrupted by water control or check structures. These check structures allow the water level to be checked up so that the water level in the lateral is sufficiently high so that the proper rate of flow can be delivered to water users at that location. These check structures have gates (so that water can pass downstream) and weirs (so that water will continue to flow downstream regardless of how the gates are set).

SRP has two types of irrigation laterals: canals and pipelines. Pipelines have headboxes that have weirs and undershot gates within the structure that serve as check structures, while canals have a simple check gate structure across the canal. As part of the project, SRP provided estimates of the water level upstream from check structures required to make deliveries (referred to as the Highwater Level). For canals, a depth below the top of the structure (TOS) was provided. For pipeline headboxes, these defined water levels and depths proved to be inconsistent. As a result, SRP decided to define the desired water level on the upstream side of pipeline headboxes as 15 cm (0.5 feet) above the weir.

One SRP requirement is that the water level at one check structure cannot be so high that it backs up on the next check structure upstream. For pipelines, SRP’s requirement is that the backwater from the downstream structure should be 6 cm (0.2 feet) below the weir in the headbox. This means that the total drop in water level at pipeline headboxes is 21 cm (0.7 feet). For canal structures, SRP requires that the backwater from the downstream structure should be 15 cm (0.5 feet) below the highwater level upstream from the structure. These criteria were used to develop estimates of lateral capacity in between check structures based on backwater curves.

Additional SRP requirements include a minimum manhole energy loss of 6 cm (0.2 feet). For channels, a minimum of 15 cm (0.5 feet) of freeboard is required, except upstream from broad‐crested weirs which can have a freeboard of only 6 cm (0.2 feet). Open channels should have an M1 backwater curve. The general requirements for a pipeline lateral are shown in Figure 6.

Upstream Downstream Allowable Weir Control Hydraulic Elevation Elevation Grade Line

Headbox

Figure 6. Schematic diagram of backwater curves showing control and allowable elevations.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

4. BACKWATER TEMPLATE

To satisfy SRP requirements under this project, WEST developed a template for the calculation of backwater curves in the various laterals. The backwater curve starts at the downstream check structure, which has one of two options:

• Downstream (D/S) Channel Headbox • Upstream (U/S) Channel Headbox

The backwater is calculated upstream through two types of elements:

• Pipeline • Channel

The backwater ends at the upstream check structure, which has two options:

• Upstream Pipeline Head Box • Upstream Channel Head Box

The section of lateral between the two headboxes is often comprised of many structures, including several sections of canal, pipeline, manholes, and various other transitions. The template was set up so that after selecting one of the components described above, the user is required to select a transition between it and another component. The following transition elements were included in the template:

• Head Box to Pipeline • Head Box to Channel • Channel to Channel • Channel to Pipeline • Pipeline to Pipeline • Pipeline to Channel • Pipeline to Head Box • Channel to Head Box • Pipe Bend • Manhole

The template system provides calculation in blocks of 10 rows. The calculations from one block to the next assumes that information will be provided in the proper cell in the block above it. At the start of each 10‐row block, the user enters the block type from a drop‐down menu. The user is responsible for assuring that the blocks are selected in the proper sequence. When the block is selected, data from the template are copied into the rows below where the block type was selected. Rows without data are automatically hidden. Once this data is copied, the user can change any of the values or change any of the calculations. This provides the user a great deal of flexibility to alter the calculations as needed to match unique situations.

The user manually enters the flow rate in Arizona Miner’s Inches (MI). Note that 1 Arizona Miner’s Inch is equal to 11.22 gallons per minute or 0.000063 cubic meters per second. The program automatically computes the energy level at each component in the system. It also calculates whether the actual freeboard satisfies SRP’s freeboard requirement and computes the difference between the actual energy level at the upstream headbox and the allowed level. If the freeboard requirement is met and the actual level is below the allowed level (positive value), then the capacity is greater than the discharge value entered. The discharge is gradually increased until the criteria is no longer met. The highest flow rate that meets the criteria within 10 MI is considered the capacity of this reach of the lateral.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

5. PROCESS

For each lateral, the process was to start at the structure defining the downstream end of each branch and compute the hydraulic grade line to the upstream structure. SRP as‐built drawings were used to determine stationing. Canal and culvert distances were determined by measurements on an aerial image. Structure elevations were determined with surveying instruments. For all canal check structures and pipeline head boxes the TOS was surveyed. These elevations were used as the basis of the calculations. The distance from the TOS to the weir crest within the headbox was provided by SRP personnel on a Service Area map (like Figure 5 or Figure 4). The project area included SRP Areas 24 and 26. For canals and drains, cross‐sections were surveyed upstream and downstream of any check structure, including top of canal and toe (or invert). These elevations were used directly in the backwater calculations.

For pipeline structures, pipe invert elevations were taken from the as-built plans. This only influenced the backwater curve if the pipe was not full or in an open channel condition, which only occurred in a few places. Because the as-built plan elevations were not considered highly accurate, no attempt was made to collect more detailed data or to more closely try to reconcile the hydraulic grade line.

SRP personnel also made note of check structures that were no longer used to control water surface elevation. When starting downstream, the calculations for a single worksheet progressed upstream until a check structure was used to control head. A single capacity was determined for each worksheet. Thus, the capacity was between these two check structures and did not always align with the capacities on SRP maps. The worksheet name is based on the downstream structure.

The procedure for determining capacity was as follows. The worksheet named “Lateral” was copied and named according to the downstream turnout. The TOS elevation from survey was entered for the downstream headbox. Then either the depth to highwater (for canals) or distance to the weir crest (for pipelines) was entered. This was used to determine the downstream energy head to start the backwater calculation. For pipelines, the pipe size, roughness, and elevations were determined from the as-built plans. For canals, cross‐section and roughness were determined from the as-built plans, but elevations were determined from survey. Structures were added from downstream to upstream either according to as-built plans, or, if as-built plans were missing, from measurements taken from aerial photos. Plan numbers were entered so that the calculation could be verified.

These calculations were carried to the upstream headbox where the TOS elevation and other details were added, similar to the downstream headbox. Note that the user enters the same information for a structure regardless of whether it is upstream or downstream. The actual backwater calculations occurred automatically, except in a few cases where manual entry is required to more accurately define conditions (e.g., where a downstream canal depth just above critical depth is entered when the calculations result in critical depth). The spreadsheet automatically summarizes the allowable head and whether or not freeboard is satisfied just below the capacity to make it easier to verify these constraints. The capacity typically started at the SRP defined capacity and then was decremented up or down. The highest capacity,in 10 MI increments, that satisfied all of SRP’s criteria was considered the calculated capacity.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

6. EXAMPLE

Figure 7 shows details for a section of Service Area 26 along Lateral 2-23 and 2-22. The number in the middle of each grid element is the section number (16). The dark blue dashed lines are pipeline laterals. The magenta solid lines are open channel laterals. The gold long dashed lines are open channel drains. The large light blue numbers along the laterals are the original SRP lateral capacities in Arizona Miner’s Inches (this study was undertaken to update these numbers). The black and green numbers with arrows are the turnout name. The gold numbers are the distance from the TOS to the high water. The red numbers are the distance from TOS to the weir.

In Figure 7, Lateral 2-22 flows along the east side of Section 16. A side branch of lateral 2-23 flows along the west side on Section 16. The Excel worksheet for the section between 2-22-75 to 2-22-74 is shown in Figure 8. Note that while on the map shown in Figure 7, the section looks like it is all canal, there is actually a short section of pipeline that is not shown on the map, which is likely a road culvert. Figure 8 shows the overall flow of the program. The discharge in MI is shown in the upper right. Below that are the head available and whether or not the freeboard is acceptable. There is also a note that says that freeboard is the limiting factor for this capacity. Note that there is still almost 0.3 m (0.972 feet) of available head. The station numbering comes from the plans. Plan numbers are usually noted in the comment section. For this example, the section of canal shown is not constrained by freeboard. The short pipe section that follows is not flowing full. In this case, the user has to assure that the energy grade line is appropriate. The sequence of elements for this example are:

1. D/S Channel Head Box, 2. Head Box to Channel, 3. Channel, 4. Channel, 5. Channel to Pipeline, 6. Pipeline, 7. Pipeline to Channel, 8. Channel, 9. Channel to Head Box, and 10. Upstream Canal Head Box.

Note that for Head Box to Channel transition, the head loss is specified and the loss coefficient is calculated. This was done to resolve optimization conflicts in computing this head loss directly.

Figure 7. A section of SRP Service Area 26 with additional details (north is up).

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

Figure 8. Spreadsheet calculations for Lateral 2-23.0.

7. RESULTS

7.1 Lateral System Capacity

The capacity of required segments of laterals from 2-15 to 2-23 were calculated and compiled into tables as shown in Figure 9. These tables show the location, the original SRP capacity (in Arizona Miner’s Inches), and the estimated capacity from the spreadsheet tool developed by WEST (also in Arizona Miner’s Inches). In addition, areas that were bottle necks were identified in the notes section of this table. For example, for Lateral 2-22, the capacity at the downstream end of the lateral is limited because of freeboard constraints.

7.2 Limits on Capacity

The results of this analysis identified several capacity constraints in the SRP lateral system between the Grand Canal and the desired delivery point for the planned water treatment plant. These are summarized below:

• The highwater elevation just upstream from turnout 2‐23‐98 limits drainage flow from the east. • The drain along 115th Avenue is limited by a crossing over a drainage structure just north of Buckeye Road. • Capacity is restricted along the branch of 2‐23 that follows 107th Avenue just north of Buckeye Road. • The capacity of the branch of lateral 2‐23 along 99th Avenue south of McDowell Road is constrained by the freeboard in concrete canals in the vicinity of turnout 2‐23‐66 just north of Buckeye Road. • The capacity of 2‐22 is limited between Buckeye Road and Lower Buckeye Road, again by canal freeboard.

3rd World Irrigation Forum (WIF3) ST-1.1 1-7 September 2019, Bali, Indonesia W.1.1.32

• The capacity of 2‐21 is limited below turnout 2‐21‐71 where the pipeline turns to a canal, roughly ½ mile south of Lower Buckeye Road and 87th Avenue. • Capacity to bring water from 2‐20 along Lower Buckeye Road is somewhat limited. • Bringing water from laterals further east is limited by the capacity constraints listed above.

Figure 9. Example capacity table developed for Lateral 2-22.

8. CONCLUSIONS

The spreadsheet template approach was an effective way to organize the large number of calculations required to evaluate lateral capacities of a network of open channel and closed pipeline laterals that extended over 193 km (120 miles). The worksheets provide a useful platform for maintaining the data in a format where calculations can be reviewed and modified as needed. The worksheets describing existing conditions can be copied and new structures added or subtracted to evaluate the influence of proposed alternatives.

Using the information provided by the spreadsheet tool, SRP was able to determine if their lateral system had sufficient capacity to carry access water to the Buckeye Feeder Canal on behalf of the City of Goodyear. In addition, SRP now has a list of bottle necks in their lateral system that they can analyze in further detail to determine if capital improvements are needed.

9. REFERENCES

Salt River Project. 2002 SRP: Delivering more than power. http://www.srpnet.com.