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Water Harvesting and Mining. Dr. Daniel O. Olago Department of Geology University of Nairobi Nairobi, Kenya. Project - Increasing Community Resilience to Drought in Makueni District 4th January 2007, Garden Hotel, Machakos. Introduction.

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water harvesting and mining

Water Harvesting and Mining

Dr. Daniel O. Olago

Department of Geology

University of Nairobi

Nairobi, Kenya

Project - Increasing Community Resilience to Drought in Makueni District

4th January 2007, Garden Hotel, Machakos

  • The main hazard that affects the Sakai Division of the Makueni District is drought.
    • For the last ten years droughts have been prolonged, frequent and severe and have had serious negative effects on the main livelihood, mixed farming, where crop production is the dominant activity.
  • This component aims to construct sand dams and wells
  • Sand dams have been a success in neighbouring Kitui District
    • in 10 years time, 65,000 people have better access to water through low cost measure at an investment of about 35 USD per capita.
    • The increased water availability results in higher farm yields, as well as for irrigated and non-irrigated crops.
    • The average income of farmers living near dams rose from near zero to Ksh. 9,000 (Lasage et al., 2006, draft paper).

Goal and Objectives

  • GOAL
    • Reduced Risk and vulnerability to climate-induced drought through participatory activities to evolve sustainable climate adaptation strategies in Kisau Division
    • To increase household food security through increased livelihood resilience and reduced vulnerability to drought in Kisau Division
    • To reduce poverty through improved livelihoods in Kisau Division
    • To facilitate integration of climate change and adaptation into policy development and planning
background climate of africa
Background- Climate of Africa
  • Global mean surface temperature is projected to increase between 1.5°C (2.7°F) and 5.8°C (10.8°F) by 2100.
  • Climate change scenarios for Africa indicate future warming across the continent ranging from 0.2°C (0.36°F) per decade (low scenario) to more than 0.5°C (0.9°F) per decade (high scenario)
  • This warming will be greatest over the interior of semiarid margins of the Sahara and central southern Africa.

Mean surface air temperature anomalies for the African continent, 1901 – 1998, expressed with respect to the 1961-1990 average; annual and 4 seasons – DJF, MAR, JJA, SON. The smooth curves result from applying a 10 yr Gaussian filter. (from Hulme et al., 2001).

rainfall in eastern africa
Rainfall in eastern Africa
  • Observed annual rainfall anomalies indicate that there are possible increases in precipitation in east Africa, contrasted with reduced precipitation for southern Africa in the next 100 years

Observed annual rainfall anomalies for three African regions, 1900-1998, and model-simulated anomalies for 2000-2099. Model anomalies are for 10 model simulations derived from seven DDC GCM experiments; the four HadCM2 simulations are the dashed curves. All anomalies are expressed with respect to observed or model-simulated 1961-1990 average rainfall. Model curves are extracted directly from GCM experiments. Smooth curves result from applying a 20-year Gaussian filter (Hulme et al., 2001).

freshwater resources
Freshwater Resources
  • The major effects of climate change on African water systems will be through changes in the hydrological cycle, the balance of temperature, and rainfall (IPCC 2001).
  • Non-climatic changes such as water policy and management practice may have significant effects.
  • Many African countries are today experiencing water stress, and it is projected that many more will shift from a water surplus state to a water scarce state by 2025 due to changes in population alone (IPCC 2001).
freshwater resources1
Freshwater Resources
  • Some of the basic problems with water as a resource in Africa include:
    • the very high potential evaporation which occurs throughout the year and is in excess of 2000 mm p.a. over large tracts,
    • very high aridity indices
    • a generally low conversion of rainfall to runoff
    • an often very concentrated seasonality of rainfall, and hence runoff,
    • a strong response to the ENSO signal and thus generally high inter-annual coefficient of variability of rainfall
    • an amplification of the inter-annual coefficient of variability of rainfall by the hydrological cycle (Schulze 2001).
  • Other problems that affect the quantity, quality and availability of freshwater include
    • increasing population pressure and pollution of water resources,
    • land use leading to enhanced erosion/siltation, and
    • possible ecological consequences of land-use change on the hydrological cycle.
  • Sand dam(s) and shallow well(s) constructed
    • Identification of suitable sites
    • Designing of dams and wells
    • Mobilization of community and capital resources
    • Construction and commissioning of the dams and wells
detailed activities carried out to date 1
Detailed Activities Carried Out to Date - 1
  • Hydrogeological survey comprised of the following investigations:
    • Morphology of the river profiles
    • Texture of the sediments contained in the channel (sands and gravel) forming part of the reservoir
    • Length of the weir/ embarkment
    • Depth and nature of the geological formations below the water reservoir

The survey was led by Mr. Kuria (University of Nairobi) guided by Mr. Isaac N. Kivindyo, Chairman Community Based Organisation (CBO) Sakai Division and accompanied by Cyprian Kaaria Mbaabu Irrigation officer and Mr. Mwoki the District Geologist, Ministry of Water and Irrigation.


Detailed Activities Carried Out to Date - 2

  • Prior to site visit the community had pre-selected 11 locations that they preferred to be considered during the reconnaissance survey.
    • The pre-selected sites included 6 sand dams, 3 earth dams and 2 springs possibly together with the wells
    • Sand dams:
      • Yiiani, Muting’u, Kawema, Muema Musango, Motomo, Ivuli Obadia
    • Earth dams:
      • Kathamba, Dick Maruta, Mukwii Kathamba
    • Wells
      • Kisilu mithanga, Nthongori well and spring

Detailed Activities Carried Out to Date - 3

  • A total of six sites were visited during the reconnaissance survey.
    • Sand dams
      • Muiu, Mutingu, Mukwii, Mutomo
    • Earth dams
      • Kathamba
    • Wells
      • Kitiani well which was found to be suitable for clustered hand dug wells.
  • Good potential for sand dams and wells

Detailed Activities - Group Discussions

  • Discussions centred on:
    • Community mobilisation on water issues
    • Preliminary site investigations results
    • Detailed survey (to be implemented)
    • Development of sand dams (to be implemented)
    • Environmental impact assessment
    • Site management post-commissioning

Next Few Months

  • Activities for:
    • Identification of 1-6 suitable sites for sand dams and wells (depending on cost)
    • Specific designing of dams and wells
    • Mobilization of community and capital resources
    • Construction and commissioning of the dams and wells