3. Organization of the watershed hydrological experimental system (WHES)

#### 3.1. Requirements of the WHES

It can be summarized based on discussions aforementioned as follows: (1) need all scales including the two extremes of pure natural and pure artificial entities, and various intermediate entities; (2) need both downward or top-down approach and upward or bottom-up approach [33], and it could be realized by strategies of constrain complexity and add complexity, respectively; (3) need the measures of manipulation for both natural and artificial entities; (4) need parallel entities of different coverages especially the plant ecosystems; and (5) need an extension of WHES. As have experienced that for identification, evaluation, and quantification of the interactions between hierarchical subsystems, it needs working on the molecular level and nuclear level for both water and its material mediums, i.e., their isotopic and hydrochemical processes. So the role of it is not merely for getting reference data but for opening another door for the understanding of the hierarchical subsystems.

#### 3.2. Organization and treatment of the WHES

2.2.6. Strategy of manipulation

240 Hydrology of Artificial and Controlled Experiments

may have two ways as experienced:

wind at their back, the measures of manipulation.

(WHES)

3.1. Requirements of the WHES

Remember the warning from Werner Heisenberg that, "what we observe is not nature herself, but nature exposed to our method of questioning," as we have experienced that for achieving our goal of watershed hydrological experimentation, tests of outrageous hydrological hypotheses, and for the generation of theories, it appears very difficult to rely only upon the natural EBs even in small scale due to its inherent complexities. However, the natural EBs are indispensable for achieving the goals. A possible solution for this knot maybe taking some actions that are compelling instead to let it be. What follows that the way of constrain complexity and add complexity is never just for the natural entities but also for the manipulated natural entities. It

1. Artificial-natural. Starting with the artificial entity, an artificial subsystem of a watershed following different designs, with/without plant systems, maybe a slope, or several combined slopes, or a catchment with slopes. Making artificial boundaries including the bottom and the surface and subsurface dividers, using filling soil or undisturbed soil to form both unsaturated zone and saturated zone. After many years of operation, such an artificial entity approaches gradually to the natural conditions including the promotion of both the physical and chemical features of soils and the ecosystem beneath the ground surface. Here, we term it as the artificial-natural, from artificial approaches to natural, e.g., the hydrohill, soil of 1 m in depth was filled up at 1978, equipped and operated at 1982, in the meantime after decades' of exposure under natural rainfalls, it's unsaturated zone can be treated as almost the natural entity. Further step of manipulation is to making around environment e.g., the rainfall input and even the microclimate to be partly controlled. 2. Controlled-natural. Starting with a selected natural EB with natural bedrock and deposit, the artificial controls are then made to it including its bottom and surroundings aimed at reducing its surface and/or subsurface inputs and outputs. Here, we term it as the controlled-natural, the natural to be controlled, e.g., the Nandadish, and it will be described in detail later. It may come down to a point that for tapping their potential, both the strategy of constrain complexity and add complexity based on the middle-ground perspective still needs to have the

3. Organization of the watershed hydrological experimental system

It can be summarized based on discussions aforementioned as follows: (1) need all scales including the two extremes of pure natural and pure artificial entities, and various intermediate entities; (2) need both downward or top-down approach and upward or bottom-up approach [33], and it could be realized by strategies of constrain complexity and add complexity, respectively; (3) need the measures of manipulation for both natural and artificial entities; (4) need parallel entities of different coverages especially the plant ecosystems; and (5) need an As schematically shown in Figure 6b, it includes three levels with both complexity and randomness from high to low, and an extension part:


There are different treatments for different organization levels of WHES as shown in Figure 6c. Only the "micro" level of WHES is linear, and a small part of the "meso" level, which is very close to the "micro" level is quasilinear or linearizable, these two parts can be treated by Newtonian dynamic methods. For the large-scale river basin, it belongs to the hydrometric monitoring network (HN) (Figure 6b), statistics will be the dominate method. In most of the intermediate chain, the "meso" level of WHES (Figure 6b) should be treated by nonlinear dynamic methods.

#### 3.3. The WHES of Chuzhou hydrology laboratory

The idea for the necessity of an experimental system for watershed hydrology [7, 34] was summarized from the decades working on field basin studies since the operation of the first hydrological experimental station in China, the Bluebrook, which was established in 1953 [35]. The dream of a WHES finally came to reality with the establishment of the Chuzhou hydrology laboratory (CHL) in 1978 by the Nanjing Hydraulic Research Institutes of the Chinese Ministry of Water Resources on the basis of the Chengxi Runoff Experimental Station established on 1962 with three experimental watersheds. This Chuzhou WHES was designed including both artificial and natural entities of different scales as shown in Figure 8a, within which, most of them have established, few of them are in modified and renewed after an interruption of many years. This WHES is settled in a natural Bloomhill (Hua-Shan) watershed (Figure 8b), with surficial drainage area of 82.1 km2 since 1962, 80.0 km<sup>2</sup> since 1998 due to a hydraulic engineering. This basin is situated at the upstream area of a river named as the Western Stream of Chuzhou, which was described in an ancient poem of Tang Dynasty by Wei Ying-Wu (737–792) which most Chinese pupil can recite. In the meantime within such a

water, air, and living organisms regulate the natural habitat and determine availability of life sustaining resources" [13]. Later in 2005, in a report of a workshop, it was further defined as an extending from "the vegetation canopy to the zone of groundwater" [36], or "the bedrock to the atmosphere boundary layer" [37]. Critical zone becomes one of the most compelling

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Aforementioned that if we designate the first phase of basin study until ca. the middle twentieth century as the stage of foundational and the second phase during/after the recommendation of EB of IHD since 1965 as the stage of developmental, a third phase of renovation seems ready to come out inevitably. What we suggested is the concept of critical zone experimental block (CZEB) [8], focusing on the fact that the natural watershed hydrological system itself, running on the principle of holism is an extending from watershed surface to its underground deposit layers, never just the dissected watershed surface laterality. The suggested CZEB geologically is a monolith block, with its surface, the watershed, bounded by topographical water divides (Figure 9) [8], it is actually an experimental "block" within the critical zone with a surface drainage basin (the watershed). It is a dynamic ecosystem coupled with various supporting systems but using hydrological processes as the unifying theme. It is a living, breathing, evolving boundary layer where rock, soil, water, air, and living organisms interact [38]. The CZEB is the watershed hydrological experimental study in the CZ observatory framework. As "the critical zone observatory network is the only type to integrate biological and geological sciences so tightly" [37]; following this, the CZEB network will perhaps be the network to integrate the hydrological, biological, and geological sciences so tightly as well.

Top: if the mean evaporation surface of the canopy is h(m) above the mean ground surface, then the top boundary of a CZEB is defined as H(m), where H ≥ (1.5–2.0) h with coefficients of h

research areas in earth sciences in the twenty-first century [14].

Figure 9. A conceptualized critical zone experimental block (CZEB) [8].

3.4.1. The boundaries of CZEB

Figure 8. (a) Organization of the Chuzhou WHES of the CHL. ND—Nandadish, GC—Gaocong, WY—Wangying, HW— Huangwa, SCH—Sanchahe, HZS—Huzhuangsan (outlet of the Bloomhill watershed), L1 to L4—lysimeters, area—surficial drainage area and (b) the natural Bloomhill (Hua-Shan) watershed within which the Chuzhou WHES is settled all ad.

traditional cultural atmosphere, the reborn CHL together with WHES is in the process of emotional renovation.

#### 3.4. What is CZEB

The "critical zone" (CZ) is defined by the National Research Council of US in 2001 as "the heterogeneous, near-surface environment in which complex interactions involving rock, soil, Practice on the Watershed Hydrological Experimental System Reconciling Deterministic and Stochastic Subjects… http://dx.doi.org/10.5772/intechopen.78721 243

Figure 9. A conceptualized critical zone experimental block (CZEB) [8].

water, air, and living organisms regulate the natural habitat and determine availability of life sustaining resources" [13]. Later in 2005, in a report of a workshop, it was further defined as an extending from "the vegetation canopy to the zone of groundwater" [36], or "the bedrock to the atmosphere boundary layer" [37]. Critical zone becomes one of the most compelling research areas in earth sciences in the twenty-first century [14].

Aforementioned that if we designate the first phase of basin study until ca. the middle twentieth century as the stage of foundational and the second phase during/after the recommendation of EB of IHD since 1965 as the stage of developmental, a third phase of renovation seems ready to come out inevitably. What we suggested is the concept of critical zone experimental block (CZEB) [8], focusing on the fact that the natural watershed hydrological system itself, running on the principle of holism is an extending from watershed surface to its underground deposit layers, never just the dissected watershed surface laterality. The suggested CZEB geologically is a monolith block, with its surface, the watershed, bounded by topographical water divides (Figure 9) [8], it is actually an experimental "block" within the critical zone with a surface drainage basin (the watershed). It is a dynamic ecosystem coupled with various supporting systems but using hydrological processes as the unifying theme. It is a living, breathing, evolving boundary layer where rock, soil, water, air, and living organisms interact [38]. The CZEB is the watershed hydrological experimental study in the CZ observatory framework. As "the critical zone observatory network is the only type to integrate biological and geological sciences so tightly" [37]; following this, the CZEB network will perhaps be the network to integrate the hydrological, biological, and geological sciences so tightly as well.

#### 3.4.1. The boundaries of CZEB

traditional cultural atmosphere, the reborn CHL together with WHES is in the process of

Figure 8. (a) Organization of the Chuzhou WHES of the CHL. ND—Nandadish, GC—Gaocong, WY—Wangying, HW— Huangwa, SCH—Sanchahe, HZS—Huzhuangsan (outlet of the Bloomhill watershed), L1 to L4—lysimeters, area—surficial drainage area and (b) the natural Bloomhill (Hua-Shan) watershed within which the Chuzhou WHES is settled all ad.

The "critical zone" (CZ) is defined by the National Research Council of US in 2001 as "the heterogeneous, near-surface environment in which complex interactions involving rock, soil,

emotional renovation.

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3.4. What is CZEB

Top: if the mean evaporation surface of the canopy is h(m) above the mean ground surface, then the top boundary of a CZEB is defined as H(m), where H ≥ (1.5–2.0) h with coefficients of h varying according to the vegetation, 1.5 for crops and grasses, 2.0 for woods, and forest. This is mainly for the purpose of energy budget and eddy covariance flux observations. H is just the lower part of the atmosphere boundary layer.

Lateral sides. There are two parts:

vapor, heat, CO2, etc. will be monitored.

boundary perpendicularly until bedrock.

3.4.2.1. Interfaces and compartment zones

3.4.2. The functioning of CZEB

separated as follows [14]:

3.4.2.2. The "reactors" of CZEB

50% of the total solar energy.

Part I: above the ground surface up to a height H as described above, delineated according to the surface topographic watershed boundary (Figure 11a). The lateral exchanges of water

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Part II: below the ground surface, it is in general defined arbitrarily except in the case of existing geological boundaries. (1) Case I: for a general CZEB, the lateral exchanges as shown schematically in Figure 9 are subjected to monitoring including water tracing, (2) Case II: for the setting of a controlled-natural entity as described above, it needs to close all the underground surroundings until bedrock aimed at constrain complexity by using of engineering methods; e.g., in Nandadish, it is ready to use steel sheet piling following its surficial

CZEB encompasses "the near-surface biosphere and atmosphere, the entire pedosphere [8], and the surface and near-surface portion of the hydrosphere and lithosphere" [14]. Within the CZEB, various processes including hydrologic, atmospheric, lithospheric, geomorphic, and geochemical processes are coupled and dynamically interrelated. To simplify the organization of various interfacing processes throughout the CZEB, compartment zones can be broadly

1. The zone aboveground surface, the "aboveground vegetation zone."

3. The saturated zone, the "saturated aquifer zone."

probably different rates and residence time of materials.

2. The unsaturated zone, the "belowground root zone and the deeper vadose zone."

There is also "an overall trend of increasing characteristic response time" [14, 40].

This layering has a general trend of increasing density with depth, has a dampening effect on state variables with depth, and an increase in distance to energy input at the soil surface [36].

Each zone will behave as a "feed-through reactor" according to Anderson et al. [41]. It follows then that there are three feed-through reactors coupled together in the CZEB (Figure 11), with

1. Reactor I. The first zone is the aboveground surface zone, which also contains aboveground vegetation up to its interface with atmosphere (Figure 11). Evaporation and plant transpiration may account for 50% or more of the total local precipitation and, use up to ca.

2. Reactor II. The second zone is the unsaturated zone, extending from the soil surface to the upper surface of the groundwater table. It consists of the whole soil profile: the O horizon (humus), A horizon (topsoil), B horizon (subsoil), and C and potentially D horizons

Bottom: the three cases are discussed below:

Case I: bedrock is situated at a relatively shallow depth from the ground surface while the regolith is shallow, too. The bottom boundary is defined as the geological boundary (Figure 10a).

Case II: bedrock is deep. The bottom boundary is defined as the plane where the tritium content of groundwater approaches zero or the detection limit of 0.7 TU (the "tritium naught line" (TNL) [39]), which is same as that of Case III (Figure 10b).

Case III: there are stratified alluvia, potentially with multiple aquifers with aquicludes and aquitards, common in flat plain areas with thick deposit and deep bedrock, up to hundreds of meters or more. Groundwater recharge to the river can be separated into sensitive, active, and passive zones. In this case, the bottom boundary of CZEB is defined as the bottom of the active recharge zone, which is also the plane of TNL (Figure 10c).

Figure 10. Boundaries of CZEB [8].

Lateral sides. There are two parts:

varying according to the vegetation, 1.5 for crops and grasses, 2.0 for woods, and forest. This is mainly for the purpose of energy budget and eddy covariance flux observations. H is just the

Case I: bedrock is situated at a relatively shallow depth from the ground surface while the regolith is shallow, too. The bottom boundary is defined as the geological boundary

Case II: bedrock is deep. The bottom boundary is defined as the plane where the tritium content of groundwater approaches zero or the detection limit of 0.7 TU (the "tritium naught

Case III: there are stratified alluvia, potentially with multiple aquifers with aquicludes and aquitards, common in flat plain areas with thick deposit and deep bedrock, up to hundreds of meters or more. Groundwater recharge to the river can be separated into sensitive, active, and passive zones. In this case, the bottom boundary of CZEB is defined as the bottom of the active

lower part of the atmosphere boundary layer. Bottom: the three cases are discussed below:

244 Hydrology of Artificial and Controlled Experiments

line" (TNL) [39]), which is same as that of Case III (Figure 10b).

recharge zone, which is also the plane of TNL (Figure 10c).

(Figure 10a).

Figure 10. Boundaries of CZEB [8].


#### 3.4.2. The functioning of CZEB

#### 3.4.2.1. Interfaces and compartment zones

CZEB encompasses "the near-surface biosphere and atmosphere, the entire pedosphere [8], and the surface and near-surface portion of the hydrosphere and lithosphere" [14]. Within the CZEB, various processes including hydrologic, atmospheric, lithospheric, geomorphic, and geochemical processes are coupled and dynamically interrelated. To simplify the organization of various interfacing processes throughout the CZEB, compartment zones can be broadly separated as follows [14]:


This layering has a general trend of increasing density with depth, has a dampening effect on state variables with depth, and an increase in distance to energy input at the soil surface [36]. There is also "an overall trend of increasing characteristic response time" [14, 40].

#### 3.4.2.2. The "reactors" of CZEB

Each zone will behave as a "feed-through reactor" according to Anderson et al. [41]. It follows then that there are three feed-through reactors coupled together in the CZEB (Figure 11), with probably different rates and residence time of materials.


5. The MC appears similar to blood vessel system and IMC to meridians and collaterals of the

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A trial for CZEB is included in the Chuzhou WHES, i.e., the Nandadish, which will be

The hydrological experimentation is actually a dialog with the hydrological nature; however, such a dialog seems not easy, it depends mostly on the adequate method of questioning, i.e., on the designed objects and the keys for it. If we designate the first phase of basin study until ca. the middle twentieth century as the foundational stage and the second phase during/after the IHD since 1965 as the developmental stage, which has been going on for more than five decades up to now, a third phase of renovation seems ready to come out inevitably. Facing with this transition of the experimental watershed hydrology, it appears worth to have a fundamental rethinking on our previous methods of dialog, which seems challenged, sometimes having a successful beginning but becoming increasingly inadapted with the dynamic nature. The inherent defects of the field basin studies have been summarized from Chinese decades' experiences in their basin studies with zigzagging process especially those based on

Facing with the hydrological complex dynamic system, a framework of watershed hydrological experimental system (WHES) is suggested, which is raised from both the viewpoints of the general system theory based on the paralleled concepts of the ancient Chinese and the Western, and that of the Middle-ground perspective philosophy on the Middle Way ("golden mean") that is also based on the paralleled concepts. Thus, the WHES is defined as an experimental system that is designed to dialog with the complex watershed hydrological nature, to drive opening of various doors of their black boxes aimed at revealing mechanisms hidden deep in the system. Three strategies have been developed for the WHES: the strategy of constrain complexity for the natural watershed, which is the downward or top-down approach, the strategy of add complexity for the physical model, which is the upward or bottom-up approach, and the strategy of manipulation for the operation of both ways including the so-called artificial-natural and the controllednatural. In fact the suggested WHES is trying to reconcile the deterministic and stochastic extremes, "opposites are complementary" as the basic Chinese philosophy have revealed.

As a trial of it, the Chuzhou WHES is ongoing. Most problems involved in WHES fall in the category of complex systems with some degree of organization. It includes three levels with both complexity and randomness from high to low, and an extension part: (1) high level: composed by pure natural EBs, defined as the "macros" of WHES, (2) intermediate level: composed by intermediate chain, the "mesos" of WHES, it includes both the controlled-natural entities and the artificial-natural entities, (3) low level: composed by pure artificial chain, the "micros" of WHES, and (4) extension of WHES: it is the laboratory for geochemical processes by

6. The general monitoring parameters in reactors are shown schematically in Figure 11c.

human body from the Chinese art of acupuncture.

described in detail later.

the concept of experimental basin system.

4. Conclusions

Figure 11. (a) Functioning of the CZEB, (b) the schematic "reactors" corresponding to CZEB, and (c) general monitoring parameters for the CZEB.

(Figure 11a). The unsaturated soil zone has been recognized as "the most complicated biomaterials on the planet" [14, 27].

3. Reactor III. The third zone is the saturated zone, extending from the groundwater table down to bedrock, including the capillary fringe (Figure 11). There are two general cases for CZEB, phreatic groundwater and confined aquifers.

#### 3.4.2.3. Functioning of reactors


A trial for CZEB is included in the Chuzhou WHES, i.e., the Nandadish, which will be described in detail later.
