1. Be familiar with the basic concepts related to diving and understand the basic elements of diving and diving aquifers.

2. Enhance the perceptual knowledge of phreatic recharge, runoff and discharge.

3. Deepen the understanding of the concepts of convection network and submersible flow system, and cultivate the comprehensive analysis ability.

Second, the experimental content

1. Observe rainfall and rainfall infiltration process.

2. Determine the shape of groundwater level.

3. Analyze the movement of groundwater basin.

4. Demonstrate the diving drift net under different conditions.

5. Design experiment: Use diving simulator to demonstrate the diving process system.

Third, experimental instruments and supplies.

1. diving demonstration instrument (see figure i4-1). The main components and functions of the instrument are as follows.

1) tank: containing homogeneous sand, simulating aquifer.

2) Rainfall device: simulating rainfall, which can artificially control the size and distribution of rainfall.

3) Simulated well: Two complete wells and two incomplete wells are respectively installed on the front (section A) and back (section B) of the instrument, and any well can be artificially simulated by pumping (injecting) water or pumping (injecting) water together.

4) Simulation of water collection corridor: The drainage of water collection corridor can be controlled manually.

5) Pressure measuring point: a pressure measuring head which is communicated with the pressure measuring tube on the pressure measuring plate and can measure any pressure measuring point; Communication with tracer injection bottles can demonstrate streamline.

6) Pressure measuring plate.

7) Tracer injection bottle.

8) Water stabilizing tank (used to stabilize the simulated river water level).

9) Peristaltic pump (used to simulate pumping).

2. Tracker. Show streamline in red ink.

3. Ruler (length 50 cm) and calculator, etc.

Figure Ⅰ 4-1Physical diagram of diving demonstration device

Fourth, the experimental steps

1. Be familiar with the structure and function of diving demonstration instruments.

The physical diagram of the diving demonstrator device is shown in figure i4-1.

2. Demonstration of rainfall infiltration and surface runoff

Turn on the rain switch and adjust the rainfall intensity manually. Keep the two rivers low for drainage. Carefully observe the process of rainfall and rainfall infiltration and the generation of surface runoff. Analysis and discussion:

1) The relationship between rainfall intensity and infiltration and surface runoff.

2) The relationship between topography and surface runoff.

3. Observe the groundwater table with infiltration conditions.

As shown in Figure I 4-2, in the phreatic aquifer, the water heads at all points on the equipotential line are equal, that is, the pressure-measuring water levels at points B, C and D are equal to those at points M, N and O on the phreatic surface respectively. Therefore, the shape of the groundwater level can be determined according to the following steps.

1) give moderate rainfall, keep the two rivers draining at the same low water level, and measure the well water level and river water level after the water level is stable, which are shown in Figure Ⅰ 4-3 in proportion.

2) Select 3-5 pressure measuring points between the river and the watershed, inject tracers, observe the streamline characteristics, analyze the distribution law of the flow network, and draw the streamline and equipotential lines on Figure 14-3.

3) Select 3 ~ 5 pressure measuring points to connect with the pressure measuring pipeline (be careful not to enter the air when connecting), measure the pressure measuring water level at the pressure measuring points, and show them in proportion in Figure Ⅰ 4-3. The horizontal line drawn from the top of the pressure measuring water level at each pressure measuring point intersects with the equipotential line where each pressure measuring point is located (each intersection point is on the diving horizon). Combined with the well water level and river water level, and the intersection of parallel lines and equipotential lines, the diving line is drawn on Figure I4-3.

Figure Ⅰ 4-2 Schematic diagram of water head at any point on the equipotential line in the phreatic aquifer (the blackened part of the piezometer is the piezometer height at the corresponding point).

4. Observe the deviation of groundwater watershed

Give moderate and even rainfall, keep two rivers draining at the same low water level, and observe the position of groundwater watershed.

Raise the water level on one side of the river, that is, raise the stable water tank on one side to observe the direction of groundwater watershed movement. Try to analyze why the watershed moves and whether it can be stable; What will happen to the groundwater watershed when the rainfall stops? After stopping the rainfall, carefully observe the change process of groundwater watershed.

5. Selective experiment content

Demonstration of the relationship between groundwater and river recharge and discharge under the influence of human activities.

Basic experimental conditions: give moderate rainfall, keep two rivers draining at the same high water level, make the groundwater level in a stable initial state, and select 3 ~ 5 pressure measuring points to inject red tracer. The specific demonstration content is as follows.

1) Drainage of water collection corridor: Turn on the switch of water collection corridor for drainage. Observe the change characteristics of streamline, and analyze the influence of drainage of water collection corridor on the recharge and discharge relationship between groundwater and river water.

2) Pump (inject) water into the complete well: restore the initial state. Insert the peristaltic pump water pipe into two complete wells respectively, and pump water at the same or different flow rates. Observe the changes of groundwater watershed and streamline shape.

3) Pumping of incomplete well: restore the initial state. Insert the peristaltic pump water pipe into two complete wells respectively, and control the equal depth pumping of two incomplete wells through the switch. Inject tracer at appropriate pressure measuring points, observe the streamline shape, and draw the groundwater streamline on Figure I 4-4. Analysis and discussion: whether the pumping capacity of two incomplete wells is equal when pumping at the same depth.

Experimental results of verbs (abbreviation of verb)

1. According to the above experimental step 3, draw the flow network diagram of this section on Figure I4-3.

2. According to the demonstration of pumping water from incomplete wells in experimental step 5, the flow network diagrams of pumping water from two incomplete wells with the same drawdown are schematically drawn in figure 14-4.

3. Thinking: For the phreatic aquifer in Hejian plot, when the river water levels are not equal, which side is the groundwater watershed? Try to analyze the reasons.

4. Describe the selected experimental results.

Design experiment of intransitive verbs (for reference)

1. For the phreatic aquifer of Hejian block, how do the characteristics of flow network and flow system change under the condition of uneven rainfall?

2. For the phreatic aquifer in Hejian plot, what will happen to the groundwater flow when a well pumps water with different intensities under the condition of moderate intensity and uniform rainfall?

3. Under what conditions can the phreatic aquifer in Hejian block form a multistage flow system (experimental diving demonstrator). Try to design an experimental scheme and demonstrate it.

Figure Ⅰ 4-3 Diving Simulation Demonstration (Part A)

Figure Ⅰ 4-4 Diving Simulation Demonstration (Part B)