Water harvesting

Overview of water harvesting

Water-Harvesting Systems water harvesting is an ancient tradition and has been used for millennia in most drylands of the world , Even in pre-Roman times, water-harvesting techniques were applied extensively in North Africa.

Evidence shows that simple water-harvesting techniques were used in southern Mesopotamia as early as 4,500 BC.

What is the water harvesting?!

(WH) has been defined as the collection of run off for its productive use (Critchley and Siegert, 1991) yet this initial definition is too general and has been more accurately defined as the process of collecting and concentrating water from runoff into a run-on area where the collected water is either directly applied to the cropping area and stored in the soil profile for immediate use by the crop (Prinz and Singh. 2000)

(WH) can be defined as the collection of water as a product of intended or planned action.

Artificial harvesting can be interpreted to be the collection by humans using some artificial means and not relying simply on natural processes (E.Yuen,M. Anda, K.Mathew & G.HO 2001)

(Mohammed Abdel Fattah Ibrahim)

(WH)defines the collection of rainwater on a specific area of the land in the form of surface run off, and this water is either used for agricultural purposes or other needs, or stored for use as needed

(WH) is a technique by which the water can be collected either surface or sub-surface to store up during wet period and used during dry period by applying a proper technique such as channel reservoir, on-farm reservoir, infiltration ditches, infiltration well, check dams, water harvesting dike etc. The water harvesting is (Kasdi Subagy onoi and Hayat Pawitan 2008)

Objectives of water harvesting

Restoring the productivity of the land, minimizing the risk of crop failure in drought-prone areas Combating

The optimal goal of water harvesting at the farm level is to create a sustainable and environmentally friendly agricultural production system and complement the existing system for water use, not replace it, and that the contributions of water harvesting be part of the integrated development plan for land and water resources, taking into account all aspects and technical, agricultural, and social inputs Economic and institutional (Abbass Theeb and Hajim Ahmed 2005)

Benefit of water harvesting

Water harvesting methods

• Mechanical methods: This method requires the necessity of preparing the ground and preparing it by cleaning, smoothing and paving it by covering it with a group of metal or plastic sheets and ensuring that water does not penetrate through it.

• Chemical methods: The chemicals in this method are an urgent need to reduce the water permeability of the soil, including sodium salts and paraffin wax.

• Water storage: This method is used if the area has a limited water source, as the surface is covered with a plastic cover after the water is confined to reduce the amounts of evaporation.

It is necessary to cover the surface of the water tank with a plastic cover to avoid water loss through evaporation Scatter some anti-evaporation chemicals

How much water can be harvested

One millimeter of rainfall on one square metre of roof yields one liter of water.

You can harvest water from any non-permeable roof type , but the roof must have gutters.

The larger your roof area, the more water you will be able to harvest. The roof type is important because you can collect more water off some roofs than others. This is called the runoff coefficient. The runoff coefficient is affected by the type of rainfall , and what time of year it rains.

Water harvesting and conservation

In many farming areas, readily available water is in short supply. Although the total annual rainfall in an area may be enough to sustain farm needs, it is often distributed very unevenly so that long dry periods are interspersed with periods of intense rainfall. In many cases, a crop is unable to use a high proportion of this water, as much of it is lost through run off or leaching. This may also cause soil erosion and loss of soil nutrients.

Water harvesting techniques gather water from an area termed the ‘catchment area’ and channel it to the cropping area or wherever it is required. Conservation techniques conserve water within the biomass and the soil by reducing run-off and keeping the water where it falls, as much as possible.

Water Resources in Iraq

Dams in Iraq

• The first big dam (Dokan) was constructed in 1959 on the Lesser Zab River Storage capacity was 6.8 billion m3. Later, dams were constructed for irrigation and power generation purposes .

• Haditha dam is almost of no use now due to the severe depletion of the Euphrates flow . in spite of River Storage capacity was 8.28 billion m3.

Ground water in Iraq

Only Estimated reserve renewed groundwater in Iraq by about (6.2) billion m3 annually, of which (930) million m3 in the Western Sahara, in terms of exploitation is still limited as Do not exceed the rate of exploitation in this region a little bit (Dryol, Hanan Hussein , 2020 )

The Iraqi government, in cooperation with UNESCO, is currently studying the country's aquifers in order to understand the best ways to exploit groundwater

Water Harvesting in Iraq

Water harvesting in Iraq is not a new technology, it was done in the Abbasid era, some projects were implemented in the West and then some of the existing water harvesting sites developed naturally.

In recent history, the development of the use of water resources in Iraq mainly began after 1921 building some large dams, irrigation projects and barrages.

( W H ) in Iraq Status and Opportunities

Water harvesting in Iraq is an old application with limited extent. Western Desert, Jazeera Desert and Eastern Valleys, are the zones were the water harvesting must be employed. Several water harvesting dams in Western Desert had built since 1970 these dams are intended to provide habitat and recharge of groundwater (Mukhalad Abdullah , Nadhir Al-Ansari and Jan Laue2020 )

There is limited opportunity to recharge groundwater in Jazeera area due to existence of gypsum layers. Many small dams were built in mountainous zone in the last two decades, some are important for agriculture expansion, but there is need to evaluate the effects on large dams feeding.

Rainfall and temperature in Iraq

Rainfall in Iraq is occurred in the winter from December to February, except in the north and northeastern parts, where the rainy season is from November to April. Average annual rainfall is estimated at 216mm, but ranges from 1200 mm in the northeast to less than 100mm over 60% of the country in the south. Winters are cool to cold, with a day temperature of about 16°C dropping at night to 2°C with a possibility of frost. Summers are dry and hot to extremely hot, with a shade temperature of over 43°C during July and August, yet dropping at night to 26°C [FAO ,2009]

The rainfall within the mountainous area is 18.3% of the total country rainfall , where the annual rain varies between 500-1200mm, 9.6% of the rainfall in the low folded area, the annual rain varies between 300-500mm, 6% of the rainfall in Jazeera desert, with annual rain of 150-400 mm,

dynamics of precipitation within

environment

WH depends on limited and uncertain rainfall, and thus understanding the

the

can influence the method of WH that would fit best in each context (Qadir et al., 2007)

The groundwater stock is affected by the consumption and availability of surface water. Withdrawal of water from wells affects the flow along the river, and any change in the flow of streams can affect the amount of available groundwater.

Therefore, if the amount of surface flow coming into Iraq from upstream countries is reduced, this will also have a significant impact on the groundwater systems (Nurit Kliot , 1994)

The most important problems of groundwater is that their problems of groundwater is that their heterogeneities of water quality in the heterogeneities of water quality in the aquifer even in the same one

Part of WH in Iraq

Water harvesting in Iraq can be founded into two main categories: small water ,harvesting dams, and natural water harvesting ponds.

Small Dams for Water Harvesting in Iraq Small dams in Iraq are in three main regions

1. Northern Area

2. Eastern Valleys

3. Western Desert.

Small dams in Northern area are either built to store water for the development of irrigation projects or in the sub-catchments of the main rivers. Developing of irrigation projects in the plains of the mountains was studied carefully; a dam like Duhok dam is a good example; many other dams were planned but not completed yet [Al-Simawi, H. 2008]

Regarding the dams that had been built in the sub-catchments, especially after 2003, there is still controversy about the feasibility of building small dams in the catchments of another major dam.

Local authorities, without consulting central government, continues planning and implementing such small dams

Water harvesting in the deserts of Iraq

These formations were naturally evolved, most of these were named after local nomenclatures.

These formations are:

1. Khabari: these are natural depressions, where some of them are with clay bed, and could store the collected water for 1-2 months. There are 73 are in Northern Desert and 22 in Southern Desert.

2. Ghidran: small natural depressions of dimensions from 10 to 500m, and depth from 1 to 5m, these are formed as trenches inside valleys.

3. Chaltat: small ponds where water collected from the surrounding hills. The total number of Ghidran, Thighab and Chaltat in Northern Desert is 77, and in Southern Desert is 57.

4. Water Springs: some water springs are in Jazeera Desert, near Tharthar Valley, but it’s not suitable for drinking, used only for agriculture to irrigate 14.8 thousand donums.

6. Faidhat: natural wide ponds on the path of valleys or at the end of valleys. Water is spreading in Faidhat, the soil of it is loamy soil, these utilized for agriculture

A case study for rainwater harvesting in Iraq

Iraq is the lowest country in the watershed of the two rivers. After the seventies the main rivers (Tigris and Euphrates and their tributaries) began to decline due to the construction of dams within the upper parts of the watersheds of the two main rivers and their tributaries and the impact of climate change for these reasons, Iraq suffers from a shortage of water Problems.

To overcome this problem or reduce its impact, the technique of harvesting water from groundwater can be used.

Water harvesting in Jordan