Green Roads for Water

Page 64

40 | Green Roads for Water

OPPORTUNITIES This chapter discusses several opportunities for using roads to improve rural water supply, especially to increase access to drinking water. • Road-water harvesting can recharge groundwater, and the development of shallow tube wells can serve to replenish drinking water. • Water harvesting using road bodies can feed surface drinking water systems, but care should be taken to ensure acceptable water quality. • Protecting and managing springs opened by road construction can provide a safe and reliable source of water (see chapter 6). Domestic water quality is always a concern, particularly when road surfaces and intensively traveled highways are used to collect drinking water. Such runoff is not typically used as domestic water, however. Water collected from roads generally originates from the entire catchment, whereas water coming directly from road surfaces plays only a minor role. Moreover, most water would be harvested with low-volume unpaved roads, owing to their dominance in rural areas. Precautions are necessary when water harvesting is undertaken near intensively used highways because of the higher risk of pollutants in the water. The potential that water captured in road-water harvesting may have high contaminant loads associated with road traffic, especially in the case of intensively used highways, is a legitimate concern. Surface and groundwater would then be susceptible to pollution from road runoff. Surface waters are particularly vulnerable because they are directly exposed to the contaminants. Pollution of groundwater tends to occur gradually given that some of the contaminants are intercepted before reaching the aquifer system, but the cleanup process is difficult and expensive. Common contaminants in highway runoff are heavy metals, inorganic salts, aromatic hydrocarbons, and solids from the road surface that result from regular highway operation and maintenance activities (FHWA 2016). In addition, road surface runoff may contain grease, oil, rust, and rubber particles from vehicle wear and tear. These materials are often washed off the highway during rainstorms. Heavy metals such as lead, zinc, iron, chromium, cadmium, nickel, and copper generally undergo physical, chemical, and biological transformations as they reach adjacent ecosystems. They are either taken up by plants or animals or are adsorbed by clay particles, or they settle as bottom sediments that could leach metals depending on the condition and sensitivity of the receiving water. Low pH levels (less than 7) trigger metal solubility and leaching (Hanes, Zelazny, and Blaster 1970). However, copper, iron, chromium, and nickel leaching are limited in natural waters where aerobic conditions are maintained (Granato, Church, and Stone 1995). Heavy metals from highway runoff are not necessarily toxic; the toxicity of water is determined by the form of metal and its availability to organisms. For instance, ionic copper is more harmful to aquatic organisms than elemental copper (Yousef et al. 1985). Similarly, ionic zinc and cadmium cause greater harm to aquatic life than their base forms. Another group of contaminants is polycyclic aromatic hydrocarbons (PAHs). These contaminants originate from asphalt pavement leachate, tire wear, lubrication oils, and grease. Increased traffic activity will generally lead to higher levels of PAHs in road surface runoff. Low-molecular-weight PAHs in runoff is indicative of a petrogenic origin, whereas the presence of


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Ethiopia

3min
pages 254-255

A.1 Making a community map

1min
page 262

15.3 Road maintenance group using work safety measures, Nepal

1min
page 256

A.2 Transect walk

1min
pages 263-265

15.2 How to engage communities in road development

4min
pages 252-253

15.1 Different stages in community engagement

12min
pages 246-250

Examples of community engagement at scale

2min
page 251

15.1 The scope for community engagement under different roads programs

5min
pages 243-244

water sector, agriculture, and universities, Malawi

1min
page 237

Note

1min
pages 239-240

Scope for community engagement

2min
page 242

for road programs

2min
page 238

Getting the process going Annex 14A. Sample supplemental terms of reference

2min
page 236

Governance for roads for water

2min
page 232

Conclusions

6min
pages 222-223

of seedlings

1min
page 220

Combining water harvesting and tree planting

3min
pages 217-218

12.2 Roadside tree barriers and dust movement

1min
page 216

Design of roadside vegetative barriers

2min
page 215

12.1 Roadside vegetation and road safety measures

1min
page 213

12.1 Tree planting and road visibility

1min
page 212

Opportunities

2min
page 209

Site selection

2min
page 211

Recommended practices

1min
page 210

11.1 Infiltration rates of different soils

7min
pages 197-199

References

1min
pages 205-206

11.3 Suitable pond side slopes for different soils

6min
pages 202-204

References

1min
page 192

Recommended practices

1min
pages 195-196

10.3 Rolling drainage dip in low-volume road

1min
page 190

Opportunities

2min
page 183

Recommended practices

8min
pages 184-187

8.1 Geotextile materials for reservoir lining

1min
page 169

Opportunities Recommended practice: River crossings as sand dams and bed

1min
page 172

9.2 Overview of nonvented drift with preventable failure features

1min
page 178

Recommended practices

13min
pages 162-168

Opportunities

2min
pages 160-161

Recommended practices and preferred options

5min
pages 149-151

7.1 Road culvert spacing and dimensions for floodplains

6min
pages 152-154

Alternative road option in floodplains: Submersible roads

1min
page 155

References

1min
pages 145-146

Opportunities

1min
page 148

Notes

2min
page 144

6.7 Technique for creating artificial glaciers in mountain areas

2min
pages 142-143

6.6 Snowshed in Alpine environment

1min
page 141

6.3 Recommended practices for spring management along roads

1min
page 138

6.4 Infiltration bunds

1min
page 136

6.2 Effect of road development on different types of springs

3min
page 137

5.2 Minimum cross-drainage opening for Bangladesh lowlands

9min
pages 110-115

routes

4min
pages 120-122

Changing the mountain environment

2min
pages 127-128

6.2 Tilted causeways

1min
page 134

6.3 Dissipation block placement on the road

1min
page 135

Opportunities

4min
pages 104-105

Recommended best practices

2min
page 106

3.1 Typical concentrations of pollutants in highway runoff

2min
page 65

4.11 Water-spreading weir, Ethiopia

1min
page 100

Kotomor, Agago (northern region, Uganda

1min
page 99

4.2 Fodder grown from road culvert water, South Gondar, Ethiopia

1min
page 87

Techniques for road-water harvesting

2min
page 89

Road safety principles

2min
page 88

Amhara, Ethiopia, 2018

1min
page 85

3.2 Roadside spring with inadequate collection reservoir, Sardinia, Italy

1min
page 76

Recommended practices

9min
pages 66-69

Opportunities

2min
page 64

Notes

1min
page 60

References

2min
pages 61-62

2.4 V-shaped floodwater spreader

4min
pages 58-59

harvesting

3min
page 57

Recommended practices

2min
page 51

References

2min
pages 43-46

The three levels of promoting resilience: Protective, adaptive, and proactive

2min
page 34

3 Drift construction in sand river bed: General section of nonvented

2min
page 33

Road safety considerations

5min
pages 41-42

The benefits and costs of roads for water

2min
page 35

1.2 Three levels of road resilience for different road elements

2min
page 37

2 Community mobilization for road-water harvesting in Amhara

2min
page 39

3 Roadside spring opened after road construction in Tigray, Mulegat

1min
page 27

Changing the paradigm: Concept and principles of roads for water

4min
pages 31-32
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