Water in Agriculture Constraints and limitations
Rainfed Area • 45% - 54% of Crops area, (0.66 M ha) • Two seasonal rainfall (spring , Autumn) • Long dry season (nearly six months) • All rainfed areas contain one component or more of traditional water harvesting techniques .
Rainfed constraints Changes in land use • Disturbances in run off areas • Population Residence expanded into rainfed area (rural areas) • Absence of zoning for agriculture Land • Terraces degradation -Land Abandonment Effect of climate change • Starting as early as 70’s with limited effect on low rainfall areas in highland and increases over the last decades: - high intensity , short duration, on small area - Rainfall occurred during dry season (Jahr), affect planting date and plant growth
Groundwater Constraints • 27% - 35% of cropped areas (0.41 – 0.45 M ha) • Over the last three decades, wells depth Increases : - ten and twenty folds (40 – 400, 800 m), Sanaa Basin, and in costal areas increases five folds (10 – 50, 100 m), (sea water intrusion) - Now, farmers grow veg. and some fruits using saline water (4 ds/m). • Cost of water abstraction increases nearly four times for the same depth.
Sayl (flood) • 7.2% - 16% of cropped area (0.09 -0.24 M ha) • Water allocation according to customary rules, less conflicts • Increases in size of run off produced in urban areas but with various level of contamination • Change in land use, transform the absorbing zone of run off to produce zone mostly in the intermountain plains (sanaa, Jahran, …. )
Controlled Floods (sayl) Controlled irrigation systems • Dams, diversion structures in the western and southern coastal areas. • 2.8% - 5.4 % of cropped area 60,000 ha • Protection of irrigated area and regulate floods. • Eliminate the need of annual consruction of traditonal deflectors Main Problems • Sedimentation • Cost of operation and maintenance • Conflict about water allocation between up streams and down stream beneficiaries
Springs (streams) • 2.% - 2.75 %, of cropped area • High discharges occur during rainy season and decreases in dry season; • Discharges vary from one liter/sec in the Yemen Volcanic Rocks to nearly 600 L/s in the Mesozoic rocks in WadiSurdud. • Water allocation, conducted according to customary rules; less conflict than sayl allocation. • Priority for water use is given to domestics usages . • Potential for improvements (storage and distribution canals)
Constraints in Agriculture water • Aquifers Depletion • Failure of local authority and related organizations to enforce water law and by-law which regulate water abstraction and wells drilling. • change in land use: population expanded over agriculture land. • Changing up stream rainfed area into irrigated ( well drilling, reservoirs), affected down streams users (dry wadi) • Effect of climate changes: Rainfall pattern, date of planting as related to moisture availability and growth periods. • Irrigation using contaminated or untreated waste water as an alternative to water scarcity. • Growing crops with low economic values