week 3 Flashcards
effects of water stress on plants
lower germination rates, stunted growth, reduced nutrient
uptake, increased vulnerability to pests and diseases, reduced leaf
size, fewer or small fruit
severity of impact of water stress depends on (savoir au moins 4-5) -9
- Crop type
- Crop variety
- Duration of stress condition
- Severity of stress condition (amount of water)
- Timing of stress condition
- Frequency of stress condition
- History of water stress
- Speed of onset of water stress conditions
- Water quality
what is irrigation?
Process of moving water from a reservoir, a groundwater well, or
a surface water body and applying it to the field using some form of
distribution mechanism (any type of application to agr fields that is administrated by articial means)
what is rainfed agriculture?
farming systems that are exclusively rainfed (near 80% of world fields)
history: irrigation was widely promoted by international organizations to aleviate ….. by improving yields
poverty
benefits of irrigation
- Farmer can control timing and volume of water applications → maintains
favourable soil moisture for plant growth - Allows for expansion of land area under cultivation
- Can increase crop yield by 100-400%
- Buffers against periods of drought (avoid water stress conditions)
- Allows for production of crops that demand more water
drwabacks of irrigation
- Some forms of irrigation → possible long-term effects on soil and water
sources that can lead to a decrease in productivity in the long-term - Irrigation development can have consequences for environment, human
health and socio-economic factors in the long-term
environmental implication of large-scale irrigation
- Waterlogging
- Salinization
- Soil compaction
- Soil erosion
- Water contamination (e.g., pesticides, nutrients) and pollution (e.g.,
eutrophication) - Plant diseases and pests (e.g., root rot)
- Over-extraction of aquifers (impacts to biodiversity, water contamination,
land subsidence) - Rising water tables
types of implications of large-scale irrigation (3
socio-economic effects, environmental, human health
human health hazards (implication of large scale irrigation) –name 3
- Contamination of drinking water (e.g., from pesticides, pathogens)
- Reduced access to drinking water
- Water pooling can lead to disease (e.g., malaria, yellow fever, dengue
fever)
socio economics effects of large sacle irrigation
Unequal access
* Could spark conflict among water users and create antagonistic
relationships among districts within shared watersheds
* Could cause population migration
* Over-extraction of freshwater → diminished reserves
how-when are the harmful impacts of irrigation significantly reduced?
when water is applied wisely according to the needs
type of water: 4 explain each type
Blue water = Water flowing freely in lakes, rivers, groundwater aquifers
Green water = Water stored as soil moisture and directly available for use
by plants
Greywater = Wastewater without fecal contamination
Black water = Wastewater with fecal contamination
Why is the quantity available from blue water source difficult to assess
Varying water levels and stream size, groundwater flows fluctuate over time due to climate, rainfall unpredictable, activities of upstream users, etc
Do crops vary in ability to tolerate saline conditions?
yes , young plants are more sensitive
water sources for irrigation (4)
1.Surface water
2. Groundwater
3. Water harvesting (rain, floodwater, fog, dew)
4. Recycled water (wastewater, storm water, drainage water, etc.)
What are the most common sources of water used for irrigation?
surface water (river, lakes, streams )
also possible to build small dam to retain more water
surface water: on what depends the quality of water
-Natural charascteristic of watershed and activities of upstream water users
-Quality varies over time and from season to season:
* Dry season → poorer quality (high concentration of contaminants,
high in sediments)
* Rainy season → improved quality (contaminants are diluted)
30% of global freshwater stored as groundwater in aquifers, what are the inconvenients (2) and benefits (1) of using groundwater for irrigation?
- Extraction not well developed in many resource-poor areas
- Usually better quality than surface water ,Filtration properties of soil profile (layers of subsoil and bedrock)
- Natural recharge rate very slow (≈0.1-3% per year)
what happens because groundwater recharge is very slow?
over-extraction
what is required to maintain critical ecological functions of watersheds?
minimum blue water flow (quantity, rate , timing, quality)
is rainwater harvesting best for full irrigation or supplemental irrigation?
supplemental
what are some advantages of rainwater harvesting?
-Water from rainy season can be used during dry season
-Often excellent quality if stored properly
-Can reduce flooding and soil erosion
Excavated earthen drepressions sited to receive water from uphill runoff-producing catchment area:
Farm ponds
what is to take in consideration when building an artificial pond?
- Catchment feeding it, quantity
and reliability of precipitation,
demand from crops, expected
losses (seepage and
evaporation), area available,
cost - Contact local authorities to see if special permits are needed
- Planning to adress: lined or unlined, placement, size…
Farm pond challenges or disadvantages
-potential concern with invasive species
-water losses due to evaporation (expecially in dry and hot climates) and seepage
(in unlined ponds-sans doublure)
-sediment load
-finding place to put removed soil
-quality concerns depending on farm (and surrouning farm) inputs
-varying water levels affects on biodiversity
-potential effects to downstream users and ecosystems
-farmers may not invest if they dont own the land and depends on labour availability and experience in the region
what is a sedimentation bassin vs a filtration marsh?
Sedimentation basin = constructed upstream of reservoir to catch coarse
sediments
* Filtration marsh = artificial marsh using aquatic plants to filter various
types of contaminants from water
constructed upstream of reservoir to catch coarse
sediments= ?
* artificial marsh using aquatic plants to filter various
types of contaminants from water =?
1= sedimentation bassin
2=filtartion marsh
name some filtration plants:
cattails, pickerelweed,arrowhead, blue flag iris
