3.2.1 Results
Fengqigou branch canal adopts the five models in this paper to distribute water, and the water distribution results are shown as follows.
Figure 4 and Fig. 5 show the start and end times of water distribution for each lateral canal in irrigation model 1 and irrigation model 2. These two models in order of upstream and downstream for the lateral canal. When the water distribution of the upstream lateral canal is finished and the flow rate in the branch canal can meet the flow rate requirement of the next lateral canal, the next canal will begin to distribute water. In the process of water distribution, water will not be distributed to the downstream canal skip an upstream canal. These two types of irrigation models are still widely used in major irrigation districts because their operation is simple without complicated logical relationships. The total water distribution time of irrigation model 1 and 2 is 127.19 h and 122.84 h.
Figure 6 shows the start and end times of water distribution for each lateral canal in the irrigation model 3, "Continuous irrigation between groups and rotational irrigation within groups" Canals within the same group are irrigated rotational, while canals between different groups are irrigated simultaneously. The model divides 19 lateral canals into 3 groups, as shown in Table 2. In the water distribution process, the water distribution duration of each group is the sum of the water distribution duration of all canals within the group. So the duration of the first group, the second group, and the third group is 120.98 h, 121.91 h, and 121.45 h respectively. The total duration of the canals is the longest of the duration in three groups, which is 121.91 h.
Table 2
Irrigation grouping of the irrigation model 3
Group of rotational irrigation | Each group contains the number of lateral canals | Time of group (h) |
First group | 4 | 9 | 10 | 12 | 13 | 14 | 15 | |
Time (h) | 17.88 | 13.71 | 16.47 | 17.64 | 21.71 | 14.03 | 19.54 | 120.98 |
Second group | 1 | 3 | 5 | 6 | 11 | 16 | | |
Time (h) | 18.99 | 14.55 | 17.52 | 22.38 | 23.18 | 25.29 | | 121.91 |
Third group | 2 | 7 | 8 | 17 | 18 | 19 | | |
Time (h) | 21.45 | 13.38 | 21.57 | 24.08 | 25.69 | 16.29 | | 121.45 |
Total time (h) | | | | | | | | 121.91 |
Figure 7 shows the start and end times of water distribution for each lateral canal in the irrigation model 4. The canals rotational irrigation between groups, and the canals in the same group are irrigated simultaneously in this model. The model divides 19 lateral canals into 6 groups, as shown in Table 3. The water distribution duration of each group is that of the canal with the longest water distribution duration in the group. The irrigation duration of each group from group 1 to group 6 is 18.99 h, 17.88 h, 21.71 h, 25.69 h, 19.54 h, and 16.98 h, respectively. The total duration of the canals is the sum duration of the six groups, which 120.79 h.The diffrence of irrigation duration for the canal in the same group is very small. If the diffrence small enough by rational optimization model, manager can operate the gate of canal at the same time, that bringing convenience to management.
Table 3
Irrigation grouping of the irrigation model 4
Group of rotational irrigation | Each group contains the number of lateral canals | Time of group (h) |
First group | 1 | 8 | 11 | | |
Time (h) | 18.99 | 17.96 | 18.54 | | 18.99 |
Second group | 3 | 4 | 12 | | |
Time (h) | 17.52 | 17.88 | 17.64 | | 17.88 |
Third group | 2 | 13 | 15 | | |
Time (h) | 21.45 | 21.71 | 20.58 | | 21.71 |
Fourth group | 6 | 16 | 17 | 18 | |
Time (h) | 22.38 | 25.29 | 24.08 | 25.69 | 25.69 |
Fifth group | 7 | 9 | 10 | | |
Time (h) | 18.56 | 17.14 | 19.54 | | 19.54 |
Sixth group | 5 | 14 | 19 | | |
Time (h) | 16.98 | 16.03 | 16.29 | | 16.98 |
Total time (h) | | | | | 120.79 |
Figure 8 shows the start and end times of water distribution for each lateral canal in the irrigation model5. As can be seen from the Fig. 6, there is no grouping concept in this model. The water distribution in the model is distribute the flow rate and time randomly under the condition of satisfying constraints. This method has a long idle timefor example, After the irrigation of canal 5 is completed, there is no canal for immediate irrigation and there is idle time, this time often occurs during the water distribution process., This is the reason why the water distribution time of this model is relatively long, which is 159.98 h.
Table 4
The flow rate of water distribution in the lateral canal
Canal name | The flow rate of model 1 (m3s− 1) | The flow rate of model 2 (m3s− 1) | The flow rate of model 3 (m3s− 1) | The flow rate of model 4 (m3s− 1) | The flow rate of model 5 (m3s− 1) |
1 | 0.5 | 0.5 | 0.5 | 0.5 | 0.4 |
2 | 0.6 | 0.6 | 0.5 | 0.5 | 0.5 |
3 | 0.5 | 0.5 | 0.5 | 0.5 | 0.4 |
4 | 0.5 | 0.5 | 0.5 | 0.5 | 0.4 |
5 | 0.8 | 0.8 | 0.7 | 0.6 | 0.7 |
6 | 0.5 | 0.5 | 0.5 | 0.5 | 0.4 |
7 | 0.6 | 0.5 | 0.6 | 0.4 | 0.5 |
8 | 0.6 | 0.5 | 0.5 | 0.6 | 0.5 |
9 | 0.5 | 0.5 | 0.5 | 0.4 | 0.4 |
10 | 0.7 | 0.8 | 0.5 | 0.8 | 0.7 |
11 | 0.5 | 0.5 | 0.4 | 0.5 | 0.4 |
12 | 0.6 | 0.5 | 0.8 | 0.8 | 0.7 |
13 | 0.7 | 0.8 | 0.8 | 0.8 | 0.8 |
14 | 0.5 | 0.8 | 0.8 | 0.7 | 0.7 |
15 | 0.5 | 0.5 | 0.5 | 0.4 | 0.4 |
16 | 0.5 | 0.5 | 0.5 | 0.5 | 0.4 |
17 | 0.5 | 0.5 | 0.4 | 0.4 | 0.5 |
18 | 0.5 | 0.5 | 0.4 | 0.4 | 0.4 |
19 | 0.6 | 0.6 | 0.5 | 0.5 | 0.6 |
Table 4 shows the flow rate of each lateral canal The flow rate is within the range of 0.6 ~ 1 times of the design flow rate, wnich meeting the constraint requirements. In the process of water distribution, each canal is irrigated with a larger flow rate, which can better exert the engineering capacity of the canal.
3.2.2 Model comparison
In order to fully explain the advantages and disadvantages of the five models, this paper discusses and analyzes the five models from the perspectives of the total duration of water distribution, the play of canal engineering ability, the leakage loss of canal water delivery, the abandoned water volume, and the operation operability of irrigation managers.
The total duration of water distribution is an important index of irrigation management. In the process of water distribution, managers hope to make a water distribution scheme with a shorter total duration. The total water distribution time of the five water distribution models is 127.19 h, 122.84 h, 121.91 h, 120.79 h, and 159.98 h, respectively. Irrigation model 4 has the shortest total water duration, while irrigation model 5 has the longest. The total water duration from irrigation model 1 to irrigation model 4 is not difference.
The operability of manager mainly considers the sequence of opening and closing gates from upstream and downstream in the water distribution process. Figure 10 reflects the opening sequence of the lateral canal in the five models. ( The greater the fluctuation of the gate opening curve, which show the more complicated the operation of managers). In irrigation model 1, each gateis opened one by one in the order of canal 1 to canal 19, and the water distribution process will not open the downstream canal gates before opening the upstream gates. The same way, in irrigation model 2 each gate is opened one by one in the order of canal 19 to canal 1. Irrigation model 3 divides all canals into 3 groups, and irrigation model 4 divides all canals into 6 groups, this type of water distribution model would cause canals with long distances between upstream and downstream to be grouped together, making the gate opening sequence curves fluctuate widely. Irrigation model 5 has the most fluctuating curves, indicating that managers need to travel frequently upstream and downstream of the branch canal to open the gates of the canal. Figure 11 reflects the closing sequence of the lateral canal in the five models. Due to the different duration of each canal, the order of closing the gates of the five models is different from the opening order, and the irrigation model 1 and irrigation model 2 no longer close the gates in the upstream and downstream order of the lateral canal.
The leakage losses of irrigation model 1 to irrigation model 5 are 28×103 m3, 27×103 m3, 33×103 m3, 36×103 m3, and 48×103 m3, respectively. The leakage loss of irrigation model 2 is the smallest. The leakage loss of irrigation model 5 is the largest, which is mainly due to the small flow rate and long distribution time of irrigation model 5.
Water abandonment refers to the amount of water that cannot be used due to the upper-level canal is not allocated to the lower-level canal. The irrigation process should reduce water abandonment to save water resources. Figure 12 reflects the branch canal diverts water at the design flow rate, the abandonment flow rate in the branch canal. Irrigation model 1, irrigation model 2, and irrigation model 3 have larger abandonment flow rate at the end of water distribution, but with shorter duration. Irrigation model 4 has a smaller abandonment flow rate during the whole distribution process. Irrigation model 5 has the highest flow rate and longer duration. The total volume of water abandoned from irrigation model 1 to irrigation model 5 is 101×103 m3, 86×103 m3, 67×103 m3, 36×103 m3, and 135×103 m3, respectively. where irrigation model 4 has the smallest volume of water abandoned, and irrigation model 5 has the largest volume of water abandoned. Irrigation model 4 divides the canal into six different groups, and each group can irrigation in the canal more fully, so the abandoned water is less. Irrigation model 5 has the largest volume of abandoned water due to idle time.