ANNEXURE A - SITE TYPES⁵

⁵ Refer to Fig. 1 and from par. D, page 5 of Project Document

The five site types along the western and eastern coasts of India have broadly been identified based on important factors as climate, tidal amplitude, water quality and soil characteristics.

ANNEXURE B - SITE SELECTION

Suitability of a particular area for pond culture of the penaeid prawn is site specific and depends upon numerous factors. The sites are to be pro-rated in terms of their technical feasibility, suitability and the likelihood of economic viability.

The site for a fishfarm shall be selected with great care since the site and its general arrangement will control the economics of operation. The following considerations shall be the guidelines in site selection.

- Gravity drainage of the ponds should be possible. Prawn culture in earth ponds require that the ponds can be drained dry after harvest. This is to enable the fishfarmer to prepare and recondition the pond soil, level the pond bottom and eliminate predators.

- Sites should be selected for fishfarms only where water of the required availability in volume and quality is available at the times needed for operating the farm. Water exchange in the required amount in percent of the pond water volume (generally 10%), done at specified times during the culture periods is the basic requirement in management. The quality of water available must such that the desired species can be raised⁶. There shall preferably be control in salinity, as there could be a reduction in production during the dry season due to increases in salinity above the upper limit and conversely, there could be a sharp decrease in salimity during the monsoon periods.

⁶ See Annexure C

- Preference should be given to sites where water supply to the farms, is by tidal energy, whether partially or fully, ispossible.

- The fishfarms should be sited primarily in areas unsuited to other agricultural uses.

- The soil in the area selected should be impervious or has the capacity to hold water in the pond compartments without appreciable loss due to seepage. Field investigations to determine surface and sub-surface soil conditions at the site should be made. A sandy clay to clayey loam is the best type for pond construction and for growing natural food at the pond bottom. Big stones or rock outcrops may make an area unsuitable. In general, a site will be suitable for the retention of water if the coefficient of permeability is less than K- 5 × 10^-6 m/sec⁷.

⁷ Refer to Annexure C

- The site, to have accessibility, should be in the vicinity of transportation routes or where the access road can be constructed economically.

- The farms will need electrical power and so the possibility and cost of connection should be considered.

- The tidal characteristics must be ascertained such as distance of tidal influence, the tide type and the tidal amplitude at the farm site. Geophysical conditions greatly affect tidal influence and amplitude at the farm site because conditions obtaining in the coastal areas of India have characteristics of a heavy build up of sand bars, sand spits and shoaling that could constrict the channel opening and/or decrease the amount of tidal amplitude available at the farm site.

- Economic and social factors shall be considered and these are:

availability of land and land use
availability of equipment and services and supplies needed for running the project
availability of construction materials
location of markets of produce and the determination of demand
availability of supplementary feeds in the required amount and at any time
availability of ice for marketing
availability of skilled and memi-skilled labourers
availability of reasonable amenities for the staff such as schools, shoppingfacilities, hospital
information on the local financing methods or on credits
political realities
peace and order

ANNEXURE C - RANGES OF WATER QUALITY PARAMETERS REQUIRED BY PENAEID SHRIMPS & THE MEANS TO ATTAIN THESE REQUIREMENTS

By knowing the physiological requirements of shrimp it should be possible to gain an insight into how to construct ponds more suitable for shrimp culture.

Temperature. Both growth and survival are effected by temperature. Generally, the rate of growth increases with temperature, but at higher temperatures mortality increases.

Temperature between 26 – 30 deg C are considered best in terms of gross production, for fast growth and high survival. Temperatures above 32 deg C should be a cause for concern.

The best way to ensure that the temperature of pond water does not become too hot is to provide deep water. Pond water depth should be at least 50 cm deep, but preferably 1.00m to provide better protection against high temperatures, against dilution as in control of salinity during heavy rains.

Oxygen. Maintenance of adequate levels of oxygen in the pond water is important for shrimp. Fishery biologists feel that when dissolved oxygen levels reach 3 ppm or below in fishfarms, remedial action is necessary.

The generalities are such that, growth is best at D.O. levels above 3 ppm and that mortalities will occur after short term exposure at dissolved oxygen levels below 1.2 ppm.

Water change, especially letting new water into the pond by pumping keep D.O. levels from falling to a critical point.

Orientation of the pond with the prevailing winds with the longer dimension of a rectangular pond more or less parallel to the wind helps raise D.O. levels due to wind action which increases surface water movement. Large ponds allow a greater sweep of wind across the pond than smaller ponds. High dikes block wind action.

Things in the water such as algae, bacteria, detritus being consumers of oxygen could cause lowering of the D.O. level. To reduce their number and correct low dissolved oxygen levels is to drain a portion of the pond water and refilling with clean water.

pH. Low water pH can affect the shrimp directly.

P. monodon grow in water with pH of 6.4 in the presence of inorganic carbon and do not suffer mortalities but their growth is reduced by 60 percent. The pH of water on, or adjacent to, the pond site should be within the range of 7.8 to 8.3.

Where new ponds are to be built where the subsoil is a potential acid sulphate soil, acid sulphate conditions develop when the subsoil is exposed. Considering the cost and time and the difficulty required to improve an acid sulphate subsoil where there is a non-acid top soil, it may be more economically favourable to design the ponds as a fully pumpfed farm in which the land excavation does not expose the subsoil and when fill material for the dike is in adequate quantity.

If ponds must be excavated, the surface layer of good soil can be used for dike construction and then rains won't wash acid from the dikes into the pond water. The pond bottom can be leached or limed to reduce or eliminate the acid condition.

Salinity. The normal salinity of water during high tide at different seasons of the year should be known. Just as important is the duration of freshwater conditions during the monsoons.

Generally, the best growth of P. monodon is obtained in salinities of 8 – 20 ppt.

If evaporation is high, there should be an adequate supply of freshwater with which to dilute the pond water to maintain proper salinity. Brackishwater or freshwater is pumped from series of well and/or deep wells located on or near the site, and brought to the ponds to obtain proper salinity.

Nitrogen compounds. Nitrate. Tests show that the growth of P. monodon is not affected by a concentration of 200 mg/L NO₃-N per liter) after 3 to 5 weeks exposure.

Nitrite. P. indicus growth is reduced by 50% over a period of 34 days when nitrite concentration was 6.4 mg NO₂-N per liter.

Ammonia. Chromic toxicity tests showed that a mean concentration of 0.45 mg NH₃-N per liter reduced growth by 50% of that of controls. Efforts must be concentrated on keeping ammonia levels low. The higher the density of both the species being cultured and the organisms cultured for food, the greater is the production of ammonia.

The simplest way to prevent the buildup of ammonia and other harmful substances is by changing water on a regular basis.

Hydrogen sulfide. Hydrogen sulfide (H₂S) in a pond is produced by the chemical reduction of organic matter which accumulates on or in the pond bottom. The bottom soil turns black and sometimes a rotten smell is discharged.

Test show that shrimp lost equilibrium when exposed to a level of 0.1 to 2.0 ppm hydrogen sulfide in water. Shrimp die at a concentration of 4 ppm.

Applications of iron oxides prevents formation of hydrogen sulfide but it is not practical to treat bottoms of ponds with FeO. Frequent changes of water would prevent the buildup of H₂S in the pond water.

Pollution. If the site is near a river, or by the back waters of enclosed bays, it is necessary to know if harmful substances are released upstream. This would include such things as pesticides, mining wastes, industrial and urban wastes. Future problems of pollution shall be anticipated.

ANNEXURE D - LABORATORY METHODS OF MEASURING SOIL PERMEABILITY BY THE KOPECKI-RING METHOD
(Source: Irrigation Canal Lining by D. B. Kraatz, FAO Land and Water Development Division, FAO Land and Water Development Series No. 1)

Laboratory tests of soil permeability vertical flow measurements may be made on samples of undisturbed materials. Laboratory tests using undisturbed samples may be helpful for locating areas of relatively higher seepage (qualitatively, not quantitatively).

The Kopecki-ring method is a simple means of determining hydraulic conductivity of undisturbed samples. In the field, a thin-walled cylinder is pressed into the soil to obtain a soil sample with an essentially undisturbed structure. The soil protruding at the lower side is cut away. A screen is placed at bottom of the sample to prevent loss of soil. A water head is fixed above the sample which is kept on a constant level. The water which flows through the sample in a fixed time is measured in a graduated cylinder. A diagram of the apparatus used is shown. Fig. 3.

The hydraulic conductivity is calculated from the formula:

Where:

K = hydraulic conductivity (m/24 h)

L = thickness of soil sample (cm)

h = water head above sample (cm)

Q = discharge (cm³/sec)

F = inner cross section of the cylinder (cm²)

v_t = viscosity of the used water (poise)

v₁₀ = viscosity of water at 10 deg C

Values of v_t for different temperatures are given:

ANNEXURE E - SEEPAGE METER FOR USE IN MEASURING HYDRAULIC CONDUCTIVITY UNDER WATER
(Source: Irrigation Canal Lining by D. B. Kraatz, FAO Land and Water Development Series No. 1, pages 44 – 49)

Seepage meters are, in principle, suitable for measuring local seepage rates in earth ponds. They are quickly and easily installed and give reasonably satisfactory results for the conditions at the test site.

Seepage meters should beiinstalled with the least possible disturbance of the bed material. It cannot be used in very gravelly soil.

The seepage meter with submerged flexible water bag is perhaps the simplest and cheapest device as regards construction as well as operation. It consists of a watertight see-page cup connected by a hose to a flexible (plastic) water bag floating on the water surface (Fig. 5).

Water flows from the bag into the cup, where it seeps through the pond subgrade area isolated by the cup. By keeping the water bag submerged, it will adapt itself to the shrinking volume so that the heads on the areas within and outside the cup are equal. The seepage rate is computed from the weight of water lost in a known period of time and the area covered by the meter.

The length of the handle and hose should be chosen according to local conditions. The cylinder should be pushed only a short distance into the subgrade in order to avoid, as far as possible, disturbance of the existing soil texture. While submerging and pushing the cylinder into the subsoil, the hose is kept open at its upper end to allow air and excess water from the cylinder to escape. When equilibrium is achieved, the hose is connected to the plastic bag containing the weighed quantity of water.

The accuracy of the measurement depends largely on the maintaining of the exact balance of pressure on the pond bottom inside and outside the meter.

ANNEXURE F - THE DOUBLE-TUBE METHOD OF MEASURING PERMEABILITY ABOVE THE WATER TABLE
(Source: Irrigation Canal Lining by D. B. Kraatz, FAO Land and Water Development Series No. 1)

The double-tube method is used in field seepage investigations for vertical flow measurements of permeability coefficient, K, in soils above the water table.

The apparatus consists of two concentric tubes which are inserted into an auger hole and covered by a lid with a standpipe for each tube (see Fig. 4). Water levels are maintained at the top of the standpipes to create a zone of positive water pressure in the soil below the bottom of the hole. The hydraulic conductivity of this zone is evaluated from the reduction in the rate of the flow from the inner tube into the soil when the water pressure inside is allowed to become less than that outside the inner tube. This is done by stopping the water supply to the inner tube (closing valve B) and measuring the rate of fall of the water level in the standpipe on the inner tube while keeping the standpipe on the outer tube full to the top. This rate of fall is less than that obtained in a subsequent measurement in which the water level in the outer-tube standpipe is allowed to fall at the same rate (by manipulating valve C) as that in the inner-tube standpipe. The difference between the two rates of fall enables the calculation of K.

Although theoretically not limited by depth, the practidepth range of this method is approximately 0.5 to 5 cm. Depending on the type of soil and the depth of the hole, tests are usually completed one or two hours after the tubes are filled with water. Approximately 200 litres of water are required per test.