Fig. 1   Proposed damsite on La Leche river at La Calzada.

LA LECHE RIVER FLOOD CONTROL PROJECT

LAMBAYEQUE, PERU

TASK 5:   ENVIRONMENTAL IMPACT ASSESSMENT

PART 3:   SECTIONS 5-8

June 29, 2009

Dr. Victor M. Ponce

Environmental Consultant

5.   ENVIRONMENTAL LEGISLATION

The central piece of applicable legislation in Peru regarding environmental impact assessment is the "Law of the National System of Environmental Impact Evaluation" (Ley del Sistema Nacional de Evaluación del Impacto Ambiental). The law has the following objectives:

  1. To establish a national system to assist in the identification, prevention, supervision, control and anticipated correction of the negative environmental impacts derived from human actions in connection with projects of economic development.

  2. To establish a uniform process encompassing requirements, steps, and scope of the environmental impact evaluation.

  3. To establish the mechanisms to assure public participation in the process of environmental impact evaluation.

The law is applicable to development projects that consist of activities or works that could cause negative environmental impacts, as specified in the law. The law requires an environmental certification for any covered project, to be issued by the competent authority. The projects are classified into three categories:

  1. Projects which do not cause negative environmental impacts of significance; therefore, requiring only a Declaration of Environmental Impact.

  2. Projects which could cause moderate environmental impacts, and for which the negative effects can be eliminated or minimized by the adoption of readily applicable measures; therefore, requiring a semidetailed Environmental Impact Study (EIS-sd).

  3. Projects of such characteristics, size, and/or location, that could produce negative environmental impacts of significance, either quantitatively or qualitatively; therefore, requiring a detailed Environmental Impact Study (EIS-d).

The law specifies the criteria for classification as follows:

  1. Protection of public health.

  2. Protection of environmental quality, including that or air, water, and soil, as well as the effect of noise, liquid and solid waste, and gaseous and radiactive emissions.

  3. Protection of natural resources, especially water, soil, flora and fauna.

  4. Protection of designated natural protected areas.

  5. Protection of ecosystems and scenic beauty.

  6. Protection of the quality of life.

  7. Protection of urban spaces.

  8. Protection of the archaeological, historical, architectural, and monumental heritage.

  9. Protection of other segments included in the national environmental policy.

The complexity and size of the La Leche river flood control project requires a detailed Environmental Impact Study (EIS-d) (Category 3). This classification is based on a careful assessment of the criteria listed above.

6.   ALTERNATIVE PLANS

The La Leche river flood control project consists of two earth dams: (1) at La Calzada, and (2) at Calicantro. La Calzada is an earth dam 59 m high, 1300 m long, and volume of 60 hm3. The dam has an upstream face of concrete of thickness 0.35 m, and an impermeable curtain made of a mix of cement and bentonite, of 0.5 m thickness and depth to rock (parent material). The La Calzada dam is an instream dam, on the La Leche river at La Calzada, about 2.5 km downstream of the confluence with of the La Leche river with Cincate Creek.

Calicantro is an earth dam 30 m high, 1600 m long, and volume of 60 hm3. The characteristics of the Calicantro dam are similar to that of La Calzada. However, Calicantro Dam is located in Rinconada Calicantro, which drains Huerequeque Creek. Thus, Calicantro dam is an off-stream dam, since it is not located on the La Leche river.

7.   ENVIRONMENTAL IMPACT ASSESSMENT

The environmental impact assessment is performed using the following two methodologies:

  • the Leopold matrix, and

  • the Battelle Environmental Evaluation System.

The Leopold Matrix is a system for the analysis and numerical weighting of probable impacts. The analysis does not produce an overall quantitative rating; instead, it consists of a set of value judgments. A primary purpose is to ensure that the impact of alternative actions is evaluated and considered in project planning (Leopold et al., 1971). A detailed description of the Leopold matrix methodology is given in Appendix I. The application to the La Leche flood control project is given in Section 7.1.

The Battelle Environmental Evaluation System is a methodology for performing environmental impact analysis developed at Battelle Columbus Laboratories by an interdisciplinary research team under contract with the U.S. Bureau of Reclamation (Dee et al., 1972; Dee et al., 1973). It is based on a hierarchical assessment of environmental quality indicators. A detailed description of the Battelle Environmental Evaluation System is given in Appendix II. The application to the La Leche flood control project is given in Section 7.2.

7.1   Application of the Leopold Matrix

The Leopold matrix is an analytical tool to evaluate the environmental impact of development projects. The methodology sets up a matrix of actions vs factors, with each action being evaluated for its effect on each factor. The actions are a list of proposed project activities which could cause environmental impact. The factors are a list of existing characteristics and conditions of the environment which could be affected by the proposed actions.

The original Leopold matrix methodology featured a comprehensive list of 100 actions and 88 factors (see Appendix I). The application to the La Leche river flood control project considers the eighteen (18) actions listed in Table 1. Five types of actions are considered: (1) project features, (2) construction operations, (3) materials extraction, (4) materials processing, and (5) project hazards.

Table 1.   Actions in the modified Leopold matrix.
(1) (2) (3)

ACTIONS

•

Proposed
actions
which
may
cause
environmental
impact

•

 10.  Project
features 		11.  Dams
12.  Spillways
13.  Canals
14.  Desilting basins
15.  Access roads
20.  Construction
operations 		21.  Blasting and drilling
22.  Cut and fill
23.  Surface excavation
24.  Subsurface excavation
30.  Materials
Extraction 		31.  Soil materials
32.  Cement
33.  Aggregates
40.  Materials
Processing 		41.  Soils
42.  Concrete
43.  Steel
50.  Project
hazards 		51.  Dam failure
52.  Slope instability
53.  Explosions

Table 2 lists seventy-three (73) factors which could be affected by the actions listed in Table 1. Factors are divided into three categories: (1) physico-chemical, (2) biological, and (3) cultural. The physico-chemical subcategories are: (1) lithosphere, (2) hydrosphere, and (3) atmosphere. The biological subcategories are: (1) terrestrial flora, (2) aquatic flora, (3) terrestrial fauna, and (4) aquatic fauna. The cultural subcategories are: (1) land use, (2) recreational, (3) aesthetic, (4) historical, (5) sociological, and (6) anthropogenic.

Table 2.   Factors in the modified Leopold matrix.
(1) (2) (3) (4)

FACTORS

•

Existing
characteristics
and
conditions
of
the
environment

•

100.
Physical
and
chemical

110.
Lithosphere 		111.  Soils
112.  Soil moisture
113.  Albedo
114.  Nutrients
115.  Land forms
120.
Hydrosphere 		121.  Surface water
122.  Groundwater
123.  Surface water quality
124.  Groundwater quality
125.  Temperature
126.  Salinity
127.  pH
128.  Redox potential
130.
Atmosphere 		131.  Precipitation
132.  Relative humidity
133.  Temperature
134.  Air quality during construction
(1) (2) (3) (4)

FACTORS

•

Existing
characteristics
and
conditions
of
the
environment

•

200.
Biological

210.
Terrestrial
Flora 		211.  Trees
212.  Shrubs
213.  Grasses
214.  Crops
215.  Microflora
216.  Endangered species
220.
Aquatic
Flora 		221.  Wetland species
222.  Endangered species
230.
Terrestrial
Fauna 		231.  Birds
232.  Mammals
233.  Insects
234.  Microfauna
235.  Endangered species
236.  Barriers
237.  Corridors
240.
Aquatic
Fauna 		241.  Fish and shellfish
242.  Benthic organisms
243.  Microfauna
244.  Endangered species
245.  Barriers
246.  Corridors
(1) (2) (3) (4)

FACTORS

•

Existing
characteristics
and
conditions
of
the
environment

•

300.
Cultural

310.
Land use 		311.  Forests
312.  Grasslands
313.  Agriculture
314.  Rural
315.  Urban
316.  Mining
317.  Wilderness
318.  Wetlands
320.
Recreation 		321.  Hunting
322.  Fishing
323.  Boating
324.  Swimming
325.  Camping and hiking
326.  Leisure
330.
Aesthetics 		331.  Scenic views
332.  Wilderness qualities
333.  Open space qualities
334.  Unique physical features
335.  Unique species
336.  Unique ecosystems
337.  Natural reserves
340.
Historical 		341.  Archaeological sites
342.  Historical sites
343.  Monuments
350.
Sociological 		351.  Lifestyles
352.  Public health
353.  Employment
354.  Population density
360.
Anthropogenic 		361.  Structures
362.  Transportation
363.  Commerce
364.  Utilities
365.  Water supply
366.  Wastewater management
367.  Solid waste management

Each action listed in Table 1 is evaluated in terms of its effect on the environmental characteristics and conditions listed in Table 2. A slash (/) is placed diagonally from upper right to lower left across each block where significant interaction is expected.

A number between 1 and 10 is placed in the upper left-hand corner to indicate the relative magnitude of the impact (1 represents the least magnitude, and 10 the greatest). Likewise, a number between 1 and 10 is placed in the lower right-hand corner to indicate the relative importance of the impact. The rating scheme quantifies the Consultant's judgment regarding the probable impacts.

Table 3 shows the Leopold matrix for the EIA of the La Leche River flood control project. The discussion following this table focuses on the impacts for cases where one or both of the assigned magnitude/importance pairs is greater than 5 (labeled in red). More detailed discussion follows when the assigned magnitude/importance pair is greater than 7.

Table 3.   Application of the Leopold matrix.
Actions ⇒ ⇒ ⇒ 11 12 13 14 15 21 22 23 24 31 32 33 41 42 43 51 52 53
Factors ⇓ ⇓ ⇓
100111 8/8 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0
112 8/8   2/2                              
113 7/7                                  
114 9/9                                  
115 3/3         5/5 5/5 5/5 5/5               4/4  
121 5/5   5/5                         2/2    
122 5/5   5/5                              
123 2/2                                  
124 2/2                                  
125 2/2                                  
126 7/7                                  
127 1/1                                  
128 3/3                                  
131 5/5                                  
132 5/5                                  
133 1/1                                  
134 2/2 2/2       7/7 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5      
Actions ⇒ ⇒ ⇒ 11 12 13 14 15 21 22 23 24 31 32 33 41 42 43 51 52 53
Factors ⇓ ⇓ ⇓
200211 2/2 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0
212 2/2                                  
213 2/2                                  
214 8/8                                  
215                                    
216                                    
221 5/5                                  
222 1/1                                  
231                                    
232                                    
233                                    
234                                    
235                                    
236                                    
237 5/5   5/5   5/5                          
241                                    
242                                    
243                                    
244                                    
245 4/4                                  
246 7/7   5/5   5/5                          
Actions ⇒ ⇒ ⇒ 11 12 13 14 15 21 22 23 24 31 32 33 41 42 43 51 52 53
Factors ⇓ ⇓ ⇓
300311 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0
312 7/7                                  
313 8/8                                  
314                                    
315                                    
316                                    
317                                    
318 1/1                                  
321 2/2                                  
322 7/7                                  
323 7/7                                  
324 7/7                                  
325 7/7                                  
326 7/7                                  
331 5/5                                  
332 2/2                                  
333 4/4                                  
334 4/4                                  
335                                    
336                                    
337 5/5                                  
341 2/2                                  
342 1/1                                  
343                                    
351 3/3                                  
352 1/1                                  
353 5/5                                  
354 2/2                                  
361                               9/9   4/4
362 2/2                             7/7   3/3
363 5/5                             5/5   2/2
364 2/2                             6/6    
365 7/7                             5/5    
366 1/1                                  
367 1/1                                  

The following actions are identified as crucial to the environmental impact assessment: (1) dams [1], (2) canals [3], (3) access roads [5], (4) dam failure [51], and (5) explosions [53]. The nineteen (19) entries with red scores are discussed below.

  1. Impact of dams on soils [11,111]: Dams will retain sands and silts, and will reduce the amount of sediments being deposited in the flood plain.

  2. Impact of dams on soil moisture [11,112]: Dams will retain water, which will be made available for irrigation, increasing soil moisture during dry periods.

  3. Impact of dams on albedo [11,113]: Dams will lower the albedo in the vicinity, causing changes in the near-ground air thermal balance. This changes have the effect of increasing rainfall (Ponce et al., 1997).

  4. Impact of dams on nutrients [11,114]: Dams will retain sediments and, therefore, the nutrients that are embedded in the sediments. Nutrient replenishment in the flood plain will be diminished.

  5. Impact of dams on salinity [11,128]: Dams and reservoirs will increase the ratio of evapotranspiration to runoff. The reduced runoff will cause an increase in the concentration of total dissolved solids, i.e., an increase in salinity.

  6. Impact of dams on crops [11,214]: Dams will have two effects on crops. The crops inundated by the reservoir(s) will be lost. However, the dam(s) will store water to irrigate downstream valley lands, with a substantial increase in total land surface area under production.

  7. Impact of dams on corridors [11,246]: Dams may inhibit wildlife corridors.

  8. Impact of dams on rural land [11,312]: Reservoirs may flood substantial portions of the land, which currently may be dedicated to grassland. This is particularly the case of Calicantro dam.

  9. Impact of dams on agriculture [11,313]: Reservoirs may flood substantial portions of the land, which currently may be dedicated to agriculture. This is particularly the case of La Calzada dam.

  10. Impact of dams on fishing [11,322]: Fishing will be possible on the reservoirs created by La Calzada and Calicantro dams.

  11. Impact of dams on boating [11,323]: Boating will be possible on the reservoirs created by La Calzada and Calicantro dams.

  12. Impact of dams on swimming [11,324]: Swimming will be possible on the reservoirs created by La Calzada and Calicantro dams.

  13. Impact of dams on camping and hiking [11,325]: Camping and hiking will be possible on the reservoirs created by La Calzada and Calicantro dams.

  14. Impact of dams on leisure [11,326]: Leisure activities will be possible on the reservoirs created by La Calzada and Calicantro dams.

  15. Impact of dams on water supply [11,365]: Dams will increase the water supply available for irrigation and domestic uses.

  16. Impact of blasting and drilling on air quality during construction [21,134]: Blasting and drilling will cause a moderate impact to air quality during construction.

  17. Impact of dam failure on structures [51,361]: Dam failure will cause catastrophic damage to structures.

  18. Impact of dam failure on transportation [51,362]: Dam failure will cause severe damage to transportation infrastructure.

  19. Impact of dam failure on transportation [51,364]: Dam failure will cause severe damage to utility infrastructure.

The six (6) entries with scores greater than or equal to 8 in Table 3 are further discussed below.

  1. Impact of dams on soils [11,111] (score 8/8): Dams will retain sands and silts. This will cause degradation of the downstream reach of the La Leche river, as clear water is released from the dam. The degradation effect will be diminished with appropriate sediment management at the damsite. The sediment retained in the dams will not reach the flood plain.

  2. Impact of dams on soil moisture [11,112] (score 8/8): Dams will retain water. This retention will change the natural distribution of precipitation. More water will go into soil moisture, and therefore, into evapotranspiration. Less water will go into runoff.

  3. Impact of dams on nutrients [11,114] (score 9/9): The reservoirs will hold sands and silts, and therefore, retain the nutrients that are embedded in the sediments. These nutrients will be sequestered and unavailable for use by plants.

  4. Impact of dams on crops [11,214] (score 8/8): The crops inundated by the reservoirs, particularly at La Calzada, will be lost. The inundated areas can be replaced by irrigated areas downstream, but the physical, chemical, and biological setting is not likely to be the same.

  5. Impact of dams on agriculture [11,313] (score 8/8): Substantial portions of the land, which currently are dedicated to agriculture, will be rendered inoperable by the flooding of the reservoir. This is particularly the case of La Calzada dam.

  6. Impact of dam failure on structures [51,361] (score 9/9): Dam failure will cause catastrophic damage to structures. The dam/reservoir should be designed with maximum security criteria. The emergency spillway(s) must be able to pass the Probable Maximum Flood in a safe manner, without overtopping the dam.

7.2   Application of the Battelle Environmental Evaluation System

The Battelle Environmental Evaluation System (EES) is based on a classification consisting of four levels (Appendix II):

  • Level I:  Categories,

  • Level II:  Components,

  • Level III:  Parameters, and

  • Level IV:  Measurements.

Each category (Level I) is divided into several components, each component (Level II) into several parameters, and each parameter (Level III) into one or more measurements. The EES identifies a total of four (4) categories, eighteen (18) components and seventy-eight (78) parameters.

Table 4 shows the complete list of categories, components, and parameters. Column 1 shows the four (4) categories, Column 2 shows the eighteen (18) components, and Column 3 shows the seventy-eight (78) parameters. The parameters labeled in red are most relevant for the present study.

The EES methodology is based on the assignment of "parameter importance units" (PIU). A total of 1000 PIUs is distributed among the 78 parameters based on value judgments. The individual PIUs are shown in Column 4 of Table 4. Effectively, for each parameter i its (PIU)i represents a weight wi.

Table 4.   Categories, components, and parameters of the Battelle EES.
(1) (2) (3) (4)
Categories Components Parameters PIUi (wi)

Ecology

Species
and
populations

1.  Terrestrial browsers and grazers 14
2.  Terrestrial crops 14
3.  Terrestrial natural vegetation 14
4.  Terrestrial pest species 14
5.  Terrestrial upland game birds 14
6.  Aquatic commercial fisheries 14
7.  Aquatic natural vegetation 14
8.  Aquatic pest species 14
9.  Sport fish 14
10.  Waterfowl 14

Habitats
and
communities

11.  Terrestrial food web index 12
12.  Land use 12
13.  Terrestrial rare and endangered species 12
14.  Terrestrial species diversity 14
15.  Aquatic food web index 12
16.  Aquatic rare and endangered species 12
17.  River characteristics 12
18.  Aquatic species diversity 14
(1) (2) (3) (4)
Categories Components Parameters PIUi (wi)

Pollution

Water

19.  Basin hydrologic loss 20
20.  BOD 25
21.  Dissolved Oxygen 31
22.  Fecal coliforms 18
23.  Inorganic carbon 22
24.  Inorganic nitrogen 25
25.  Inorganic phosphate 28
26.  Pesticides 16
27.  pH 18
28.  Stream flow variation 28
29.  Temperature 28
30.  TDS 25
31.  Toxic substances 14
32.  Turbidity 20

Air

33.  Carbon monoxide 5
34.  Hydrocarbons 5
35.  Nitrogen oxides 10
36.  Particulate matter 12
37.  Photochemical oxidants 5
38.  Sulfur dioxide 10
39.  Other 5

Land

40.  Land use 14
41.  Soil erosion 14
Noise 42.  Noise 4
(1) (2) (3) (4)
Categories Components Parameters PIUi (wi)

Aesthetics

Land

43.  Geologic surface material 6
44.  Relief and topographic character 16
45.  Width and alignment 10

Air

46.  Odor and visual quality 3
47.  Sounds 2

Water

48.  Appearance 10
49.  Land and water interface 16
50.  Odor and floating materials 6
51.  Water surface area 10
52.  Wooded and geologic shoreline 10

Biota

53.  Animals - domestic 5
54.  Animals - wild 5
55.  Diversity of vegetation types 9
56.  Variety within vegetation types 5
Manmade objects 57.  Manmade objects 10

Composition

58.  Composite effect 15
59.  Unique composition 15
(1) (2) (3) (4)
Categories Components Parameters PIUi (wi)

Human
interest

Educational/ scientific packages

60.  Archaeological 13
61.  Ecological 13
62.  Geological 11
63.  Hydrological 11

Historical packages

64.  Architecture and styles 11
65.  Events 11
66.  Persons 11
67.  Religions and cultures 11
68.  Western frontier 11

Cultures

69.  Indians 14
70.  Other ethnic groups 7
71.  Religious groups 7

Mood/ atmosphere

72.  Awe-inspiration 11
73.  Isolation/solitude 11
74.  Mystery 4
75.  Oneness with nature 11

Life
patterns

76.  Employment opportunities 13
77.  Housing 13
78.  Social interactions 11

Each (PIU)i or wi requires a specific measurement or assessment. The methodology converts these measurements into common units by means of a scalar or "value function." A scalar has a measurement in the x-axis, and a common environmental quality scale or "value" in the y-axis. The latter varies in the range 0 ≤ Vi ≤ 1. A value of Vi = 0 indicates very poor quality, while Vi = 1 indicates very good quality. Values of Vi = Vi, 0 are obtained for conditions 'without' the project, and Vi = Vi, 1 for conditions 'with' the project. The condition 'without' the project represents the current condition, while that 'with' the project represents the predicted future condition (see Appendix II).

The environmental impact EI of the project is evaluated as the difference between 'with' and without' conditions:

EI = ∑ [ Vi, 1 wi ] - ∑ [ Vi, 0 wi ] (1)

Since the weights are the same for conditions 'with' and 'without' the project:

EI = wi ∑ [ Vi, 1 - Vi, 0 ] (2)

Defining the impact value as:

ΔVi = Vi, 1 - Vi, 0 (3)

Then:

EI = ∑ [ wi ΔVi ] (4)

for i = 1 to n, where n = number of parameters (78).

For EI > 0, the situation 'with' the project is better than 'without' the project, indicating that the project has positive environmental benefits. Conversely, for EI < 0, the situation 'with' the project is worse than 'without' the project, indicating that the project has negative environmental benefits, i.e., certain negative impacts. A large negative value of EI indicates the existence of substantial negative impacts.

Table 5 shows the application of the Battelle EES. Columns 1-4 are the same as in Table 4. Column 5 is Vi, 0; Col. 6 is Vi, 1; Col. 7 is ΔVi; and Col. 8 is wi ΔVi. The value-function estimates are described in Appendix III. Table 5 shows that the environmental impact EI = -26.8. This value is 2.68% of the total parameter allocation, which is 1000 (see Table 1 of Appendix II). This percentage represents the change in environmental quality with project implementation. Since the value is negative, there will be a cumulative negative impact. However, the value is small and manageable with an appropriate mitigation plan in place.

Table 5.   Application of the Battelle Environmental Evaluation System (EES).
(1) (2) (3) (4) (5) (6) (7) (8)
Categories Components Parameters wi Vi,0 Vi,1 ΔVi wi ΔVi

Ecology

Species
and
populations

1.  Terrestrial browsers and grazers 14 1.0 0.7 -0.3 -4.2
2.  Terrestrial crops 14 0.7 0.9 0.2 2.8
3.  Terrestrial natural vegetation 14 1.0 0.7 -0.3 -4.2
4.  Terrestrial pest species 14 1.0 1.0 0 0
5.  Terrestrial upland game birds 14 0.7 1.0 0.3 4.2
6.  Aquatic commercial fisheries 14 0.0 0.3 0.3 4.2
7.  Aquatic natural vegetation 14 0.2 0.5 0.3 4.2
8.  Aquatic pest species 14 1.0 1.0 0 0
9.  Sport fish 14 0.2 0.8 0.6 8.4
10.  Waterfowl 14 0.5 1.0 0.5 7.0

Habitats
and
communities

11.  Terrestrial food web index 12 1.0 1.0 0 0
12.  Land use 12 0.8 0.0 -0.8 -9.6
13.  Terrestrial rare and endangered species 12 1.0 1.0 0 0
14.  Terrestrial species diversity 14 1.0 1.0 0 0
15.  Aquatic food web index 12 0.2 0.8 0.6 7.2
16.  Aquatic rare and endangered species 12 1.0 1.0 0 0
17.  River characteristics 12 1.0 0.0 -1.0 -12.0
18.  Aquatic species diversity 14 0.2 0.8 0.6 8.4
(1) (2) (3) (4) (5) (6) (7) (8)
Categories Components Parameters wi Vi,0 Vi,1 ΔVi wi ΔVi

Pollution

Water

19.  Basin hydrologic loss 20 1.0 0.2 -0.8 -16.0
20.  BOD 25 1.0 0.9 -0.1 -2.5
21.  Dissolved Oxygen 31 1.0 0.9 -0.1 -3.1
22.  Fecal coliforms 18 1.0 1.0 0 0
23.  Inorganic carbon 22 1.0 1.0 0 0
24.  Inorganic nitrogen 25 1.0 1.0 0 0
25.  Inorganic phosphate 28 1.0 1.0 0 0
26.  Pesticides 16 1.0 0.9 -0.1 -1.6
27.  pH 18 1.0 1.0 0 0
28.  Stream flow variation 28 1.0 0.2 -0.8 -22.4
29.  Temperature 28 1.0 0.6 -0.4 -11.2
30.  TDS 25 1.0 0.7 -0.3 -7.5
31.  Toxic substances 14 1.0 1.0 0 0
32.  Turbidity 20 1.0 1.0 0 0

Air

33.  Carbon monoxide 5 1.0 1.0 0 0
34.  Hydrocarbons 5 1.0 1.0 0 0
35.  Nitrogen oxides 10 1.0 1.0 0 0
36.  Particulate matter 12 1.0 0.9 -0.1 -1.2
37.  Photochemical oxidants 5 1.0 1.0 0 0
38.  Sulfur dioxide 10 1.0 1.0 0 0
39.  Other 5 1.0 1.0 0 0

Land

40.  Land use 14 1.0 0.9 -0.1 -1.4
41.  Soil erosion 14 1.0 0.8 -0.2 -2.8
Noise 42.  Noise 4 1.0 0.8 -0.2 -0.8
(1) (2) (3) (4) (5) (6) (7) (8)
Categories Components Parameters wi Vi,0 Vi,1 ΔVi wi ΔVi

Aesthetics

Land

43.  Geologic surface material 6 1.0 1.0 0 0
44.  Relief and topographic character 16 1.0 1.0 0 0
45.  Width and alignment 10 1.0 0.8 -0.2 -2.0

Air

46.  Odor and visual quality 3 0.6 0.6 0 0
47.  Sounds 2 1.0 1.0 0 0

Water

48.  Appearance 10 0.1 1.0 0.9 9.0
49.  Land and water interface 16 1.0 0.8 -0.2 -3.2
50.  Odor and floating materials 6 1.0 0.9 -0.1 -0.6
51.  Water surface area 10 0.1 1.0 0.9 9.0
52.  Wooded and geologic shoreline 10 0.1 1.0 0.9 9.0

Biota

53.  Animals - domestic 5 1.0 1.0 0 0
54.  Animals - wild 5 1.0 1.0 0 0
55.  Diversity of vegetation types 9 1.0 0.8 -0.2 -1.8
56.  Variety within vegetation types 5 1.0 0.8 -0.2 -1.0
Manmade objects 57.  Manmade objects 10 1.0 0.8 -0.2 -2.0

Composition

58.  Composite effect 15 0.7 1.0 0.3 4.5
59.  Unique composition 15 1.0 0.9 -0.1 -1.5
(1) (2) (3) (4) (5) (6) (7) (8)
Categories Components Parameters wi Vi,0 Vi,1 ΔVi wi ΔVi

Human
interest

Educational/
scientific packages

60.  Archaeological 13 1.0 0.9 -0.1 -1.3
61.  Ecological 13 1.0 1.0 0 0
62.  Geological 11 1.0 0.9 -0.1 -1.1
63.  Hydrological 11 1.0 1.0 0 0

Historical
packages

64.  Architecture and styles 11 1.0 1.0 0 0
65.  Events 11 1.0 1.0 0 0
66.  Persons 11 1.0 1.0 0 0
67.  Religions and cultures 11 1.0 1.0 0 0
68.  Western frontier 11 1.0 1.0 0 0

Cultures

69.  Indians 14 1.0 1.0 0 0
70.  Other ethnic groups 7 1.0 1.0 0 0
71.  Religious groups 7 1.0 1.0 0 0

Mood/
atmosphere

72.  Awe-inspiration 11 1.0 1.0 0 0
73.  Isolation/solitude 11 1.0 1.0 0 0
74.  Mystery 4 1.0 1.0 0 0
75.  Oneness with nature 11 1.0 1.0 0 0

Life
patterns

76.  Employment opportunities 13 0.3 1.0 0.7 9.1
77.  Housing 13 1.0 0.5 -0.5 -6.5
78.  Social interactions 11 0.3 1.0 0.7 7.7
 The Battelle EES Environmental Impact Analysis Cumulative Index EI ⇒ -26.8


In the Battelle EES, the potential problem areas are represented by those parameters for which the Vi value changes significantly in the adverse direction, as measured by the following relation (negative values, in percent):

ΔVi,r = 100 (Vi, 1 - Vi, 0) / Vi, 0 (5)

These parameters are tagged with 'red flags' to indicate potential problems which may warrant more detailed attention. For parameters in the ecology category, a minor red flag applies when 5% < ΔVi,r ≤ 10%, and a major red flag when ΔVi,r > 10 %. In all other categories, a minor red flag applies when ΔVi,r ≤ 30% or ΔVi ≤ 0.1, and a major red flag when ΔVi,r > 30% or ΔVi > 0.1.

Table 6 identifies the red flags associated with substantially negative impacts of the project. A total of sixteen (16) major red flags are identified.

Table 6.   Identification of red flags.
(1) (2) (3) (4) (5) (6) (7)
Parameters wi Vi,0 Vi,1 ΔVi ΔVi,r Red flag
1.  Terrestrial browsers and grazers 14 1.0 0.7 -0.3 -30 Major
3.  Terrestrial natural vegetation 14 1.0 0.7 -0.3 -30 Major
12.  Land use 12 0.8 0.0 -0.8 -100 Major
17.  River characteristics 12 1.0 0.0 -1.0 -100 Major
19.  Basin hydrologic loss 20 1.0 0.2 -0.8 -80 Major
20.  BOD 25 1.0 0.9 -0.1 -10 Minor
21.  Dissolved Oxygen 31 1.0 0.9 -0.1 -10 Minor
26.  Pesticides 16 1.0 0.9 -0.1 -10 Minor
28.  Stream flow variation 28 1.0 0.2 -0.8 -80 Major
29.  Temperature 28 1.0 0.6 -0.4 -40 Major
30.  TDS 25 1.0 0.7 -0.3 -30 Major
36.  Particulate matter 12 1.0 0.9 -0.1 -10 Minor
40.  Land use 14 1.0 0.9 -0.1 -10 Minor
(1) (2) (3) (4) (5) (6) (7)
Parameters wi Vi,0 Vi,1 ΔVi ΔVi,r Red flag
41.  Soil erosion 14 1.0 0.8 -0.2 -20 Major
42.  Noise 4 1.0 0.8 -0.2 -20 Major
45.  Width and alignment 10 1.0 0.8 -0.2 -20 Major
49.  Land and water interface 16 1.0 0.8 -0.2 -20 Major
50.  Odor and floating materials 6 1.0 0.9 -0.1 -10 Minor
55.  Diversity of vegetation types 9 1.0 0.8 -0.2 -20 Major
56.  Variety within vegetation types 5 1.0 0.8 -0.2 -20 Major
57.  Manmade objects 10 1.0 0.8 -0.2 -20 Major
59.  Unique composition 15 1.0 0.9 -0.1 -10 Minor
60.  Archaeological 13 1.0 0.9 -0.1 -10 Minor
62.  Geological 11 1.0 0.9 -0.1 -10 Minor
77.  Housing 13 1.0 0.5 -0.5 -50 Major


7.3   Mitigation measures

Mitigation measures are planned and implemented with the objective to reduce, minimize, and/or neutralize the negative impacts that have been identified in the EIA. In some cases, mitigation measures will be effective in reducing the impact; in other cases, it may be difficult to reduce the magnitude of the impact. A few net losses are deemed an accepted compromise for the social and economic benefits to accrue from the project.

Table 7 describes a set of mitigation measures for the parameters tagged with major red flags in Table 6.

Table 7.   Mitigation measures for parameters with major red flags.
(1) (2)
Parameter Mitigation measure(s)
1.  Terrestrial browsers and grazers The reduction in the number of grazing animals due to reservoir inundation cannot be readily mitigated. One possibility is to designate alternate areas for grazing, to replace the areas lost to inundation. This is particularly significant in the case of Calicantro.
3.  Terrestrial natural vegetation The reduction in the number of specimens of natural vegetation cannot be readily mitigated. The loss of this natural resource is considered to be a trade-off for the economic benefits to accrue from the project.
12.  Land use The loss of agricultural lands at La Calzada and grazing lands at Calicantro will have to be appropriately compensated. This loss is considered to be the trade-off for the economic benefits to accrue from the project.
17.  River characteristics The rivers' natural characteristics will be lost once the reservoirs are in place. This will cause significant changes in the hydrobiology of the streams, both positive and negative. The loss of the swiftness characteristics of streamflow cannot be readily mitigated. It is considered to be a trade-off for the economic benefits to accrue from the project.
19.  Basin hydrologic loss The project will cause a major conversion of runoff to evapotranspiration. This will cause increased salinity in the land, imposing the need for additional drainage. This effect can be mitigated by reserving a certain portion of the natural runoff to carry the salts to the sea or, in this case, to appropriate sinks such as the La Niña lake.
28.  Stream flow variation The project operation will attenuate and reduce most floods. The effect will be both positive and negative; on the one hand, flood damages will be reduced; on the other hand, basin flushing will be compromised. This effect can be mitigated by a program of periodic artificial floods to reset the basin, partially emulating the work of Nature.
29.  Temperature Water will be retained in the reservoirs, and this water will gradually increase in temperature in the tropical climate of Lambayeque. This will change the hydrobiology of the waterbody. This effect cannot be readily mitigated.
(1) (2)
Parameter Mitigation measure(s)
30.  TDS The concentration of total dissolved solids will increase as water naturally destined to runoff is converted to evapotranspiration, leaving the salts behind. This effect can be mitigated with a program of agricultural drainage. However, a certain portion of the runoff will have to be reserved to carry the waste solids to the ocean or to an appropriate sink.
41.  Soil erosion The retention of sediments in the dams, particularly at La Calzada, will produce "hungry" water, which will have the tendency to pick up sediments as it flows downstream. This effect can be mitigated by operating the two reservoirs to minimize agradation and degradation. The need for judicious sediment management is a trade-off for the economic benefits to accrue from the project.
42.  Noise Some noise will occur during construction. It is very difficult to mitigate this effect. The noise will abate as the project is completed.
45.  Width and alignment The width and alignment of the developed waterbodies will be markedly affected by the project. There is no way to mitigate this impact. The loss of this natural aesthetic resource is considered to be a trade-off for the economic benefits to accrue from the project.
49.  Land and water interface The land and water interface will be degraded during reservoir drawdown operations. To mitigate this effect, the reservoir operations should be planned to minimize drawdowns, or to take appropriate action to reduce impacts during scheduled drawdowns.
55.  Diversity of vegetation types The loss of vegetation diversity due to reservoir placement cannot be mitigated. The loss of this natural aesthetic resource is considered to be a trade-off for the economic benefits to accrue from the project.
56.  Variety within vegetation types The loss of variety within vegetation types due to reservoir placement cannot be mitigated. The loss of this natural aesthetic resource is considered to be a trade-off for the economic benefits to accrue from the project.
57.  Manmade objects The reduction in aesthetics due to manmade objects cannot be readily mitigated. One possibility that has been tried in smaller structures is to design them so that they are less obtrusive to the eye. To the extent possible, landscaping should be used as a way of providing a pleasing view of the facility and its surroundings.
77.  Housing Local housing will be significantly affected by the project due to inundation. Compensation and relocation of the affected parties to suitable areas is a fundamental necessity of project development.


7.4   Mitigation plan

The mitigation plan focuses on the following actions:

  1. Mitigation for the flooding of croplands and grazelands at the reservoir sites.

  2. Mitigation for the flooding of rural settlements at the reservoir sites.

  3. Mitigation for the conversion of runoff to evapotranspiration and consequent increases in salinity.

  4. Mitigation for decreases in streamflow variability which may affect channel morphology.

  5. Mitigation for the downstream channel degradation caused by the release of mostly sediment-free water.

8.   SUMMARY

An environmental impact assessment (EIA) study of the La Leche river flood control project is described. The project aims to enhance flood control and water conservation in the watershed of the La Leche river, which has suffered major floods caused by the El Niño phenomenon. The proposed actions are the construction of two dams, one to retain floodwaters and the other to store water for irrigation and domestic water supply. The flood-control earth dam spans a natural valley constriction at La Calzada. The seasonal and multi-annual storage dam spans the valley of neighboring Rinconada Calicantro to the west of La Calzada.

The environmental impact assessment is performed using the following two well-established methodologies:

  • the Leopold matrix, and

  • the Battelle Environmental Evaluation System.

The development of the Leopold matrix is described in Section 7.1. The study has identified the following major impacts:

  1. Impact of dams on soils: Dams will retain sands and silts. This will cause degradation of the downstream reach of the La Leche river, as clear water is released from the dam into the channel.

  2. Impact of dams on soil moisture: Dams will retain water. This retention will change the natural distribution of precipitation. More water will go into soil moisture, and therefore, into evapotranspiration.

  3. Impact of dams on nutrients: The reservoirs will hold sands and silts, and therefore, retain the nutrients that are embedded in the sediments. These nutrients will be sequestered and unavailable for use by plants.

  4. Impact of dams on crops: The crops inundated by the reservoir(s) will be lost. The inundated areas can be replaced by irrigated areas downstream, but the physical, chemical, and biological settings is not likely to be the same.

  5. Impact of dams on agriculture: Substantial portions of the land, which currently are dedicated to agriculture, will be rendered inoperable by the flooding of the reservoir.

  6. Impact of dam failure on structures: Dam failure will cause catastrophic damage to structures. Therefore, the dam/reservoir should be designed using maximum security criteria (Probable Maximum Flood).

The Battelle Environmental Evaluation System is described in Section 7.2. The application of the methodology has produced a cumulative index of envrionmental impact EI = -26.8. The negative value indicates that the cumulative impact will be adverse. However, the small relative magnitude of EI indicates that the impact will be readily subject to mitigation.

The EES has red-flagged the following major negative impacts (Table 6):

  1. Impact on terrestrial grazers and natural vegetation.

  2. Impact on land use.

  3. Impact on river characteristics.

  4. Impact on basin hydrology.

  5. Impact on streamflow variation.

  6. Impact on water temperature.

  7. Impact on quantity of total dissolved solids.

  8. Impact on channel degradation.

  9. Impact on noise.

  10. Impact on landscape aesthetics.

Mitigation measures are identified. Plans are formulated to mitigate the major negative impacts that may be produced by the project.

APPENDIX

I.   The Leopold Matrix for Evaluating Environmental Impact.

II.   The Battelle Environmental Evaluation System for Water Resource Planning.

II.   The EES value functions.

REFERENCES

Dee, N., J. Baker, N. Drobny, K. Duke, and D. Fahringer. 1972. Environmental evaluation system for water resource planning (to Bureau of Reclamation, U.S. Department of Interior). Battelle Columbus Laboratory, Columbus, Ohio, January, 188 pages.

Dee, N., J. Baker, N. Drobny, K. Duke, I. Whitman, and D. Fahringer. 1973. An environmental evaluation system for water resource planning. Water Resources Research, Vol. 9, No. 3, June, 523-535.

Gobierno del Perú. 1969a. Ley General de Aguas. Decreto Ley No. 11752.

Gobierno del Perú. 1969b. Reglamento de los Títulos I, II y II de la Ley General de Aguas (Decreto Ley No. 11752), Decreto Supremo No. 261-69-AP.

Gobierno del Perú. 2001. Reglamento de Estándares Nacionales de Calidad Ambiental del Aire. Decreto Supremo No. 074-2001-PCM.

Gobierno del Perú. 2003. Reglamento de Estándares Nacionales de Calidad Ambiental para Ruido. Decreto Supremo No. 085-2003-PCM.

Leopold, L. B., F. E. Clarke, B. B. Hanshaw, and J. E. Balsley. 1971. A procedure for evaluating environmental impact. U.S. Geological Survey Circular 645, Washington, D.C.

Pardo, A., and V. Sanz. 1979. Estratigrafia del curso medio del Rio La Leche, Departamento de Lambayeque. Boletin de la Sociedad Geologica del Perú, No. 60, Abril, 251-266.

Ponce, V. M., and A. V. Shetty. The facts about El Niño. (http://elnino.sdsu.edu) (090515).

Ponce, V. M., A. K. Lohani, and P. T Huston. 1997. Surface albedo and water resources: The hydroclimatological impact of human activities. Journal of Hydrologic Engineering, ASCE, Vol. 2 No. 4, October.

Ponce, V. M. 2008. La Leche River Flood Control Project: Third Project Report--Final (Hydrology), July 2, 2008. [090424].

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