This post discusses water requirements for traditional gas stove/ induction pressure cookers. By traditional we mean to say the pressure cookers with a pressure vent mounted with a whistle which blows off when operating pressure is reached inside the cooker. It also has a safety valve and gasket around the lid to seal the lid and cooker body tightly. It can also be used as a reference guide along with ones judgement for other versions of traditional pressure cooker as well. Here we are going to discuss the amount of water needed to cook different food items.
Right amount of water plays an important role in the recipe as too much water can kill the flavour and less water can burn the food or melt the safety valve. Some amount of water is always needed to create steam to cook food. Different food items need different amount of water/ liquid depending on the amount of liquid they have in them.
Some amount of water gets evaporated during cooking, hence ensure there is some water added in the beginning. Amount of liquid or water needed for cooking depends on the type of food item, its size not the quantity and the size of pressure cooker.
As a general rule, for cookers with

1. Volume ranging from 1.5 litres to 3 litres, one cup of water is needed for 10 minutes of cooking time. For every extra 10 minutes add 1/2 cup of more water.
2. For volumes in range of 3.5 litres to 6 litres, 1 1/2 cups of water should be used for 10 minutes of cooking and extra 1/2 cups for additional 10 minutes of cooking.
3. For 6.5 litres to 12 litres, 2 cups of water should be used for 10 minutes of cooking and for subsequent extra 10 minutes of cooking 1/2 cup of water should be added.

It is advisable to soak beans and other dry grains overnight for faster cooking and be more digestible. In order to avoid frothing add 1-2 tsp of oil in the water and stir it well, let the water come to first boil after which close the cooker lid. Let the cooker come to full operating pressure and give first whistle after which reduce the heat between medium to lower range. If the flame is kept on high even after first whistle, the water may evaporate quickly without cooking the food and may even burn it. However, one should note that flame of the gas should be on higher side  in the beginning to achieve full operating pressure and the whistle.
Salty and acidic food items like ketchup, lemon juice, vinegar makes skin of beans harder and increases the cooking time. Hence it is advised that these items should be added only after pressure cooking is done.
As we know that dry grains grow in size after cooking. In case of rice, 1 cup of rice yields 2-3 cups of cooked rice. The amount of water needed for one cup of rice is around a little bit more than one cup of water. For exact water quantity pls refer below:

Pressure cooker size in litres	Item (1 cup)	Water needed in cups
1.5	Basmati	1 1/4
2, 3, 3.5, 4, 5, 6.5, 8, 10, 12	Basmati	1 1/8

Legumes (Beans and lentils).
Always put at least 1 1/2 cups of water for cooking legumes. Never reduce water beyond this.  Most varieties of  legumes yield 2 1/2 cups of cooked beans for every 1 cup of dry legumes. As a general rule for all legumes, 3 cups of water is needed to cook for every 1 cup of beans. Further changes in water needed can be made after some experience.
Do not fill cooker more than half as legumes rise in size after absorbing water. Always soak beans for at least 8-10 hrs before cooking.
Below mentioned is the water requirement for small size cookers whose max capacity is less than 1 cup. For pressure cooker size of 1.5 litres: maximum capacity is 1/2 cup.

Item	Water in cups (soaked and unsoaked)
Black eyed beans	1 1/2 cup – 2 cups
chickpeas	1 1/2 cup – 2 cups
Kidney beans, red beans, pinto beans, black beans	1 1/2 cup – 2 cups
Lentils	1 1/2 cup – 2 cups
Soybeans	1 1/2 cup – 2 cups

For 2 litres cooker: Max capacity for legume is 3/4 cup

Item	Water in cups (soaked)	Water in cups (unsoaked)
Black eyed beans,	11/2 cup	2 1/2cup
chickpeas	1 1/2	2 1/2
Kidney beans, red beans, pinto beans, black beans	2	3
Lentils	2 3/4	2 3/4
Soybeans	2	2 1/4

Vegetables:
For most of the vegetables 1/2 to 1 cup of water is enough and they cook in 1-2 minutes of putting the cooker on heat.

Same goes for seafood , around 3/4 cups of water is enough to cook them. Time needed to cook seafood in a pressure cooker is also very small which is around 2-3 minutes. Since seafood loses flavour if they are overcooked hence try to time accurately, take the cooker off from the gas immediately and release pressure.

Meat and poultry:
Water needed to cook meat and poultry is around 1 – 1 1/2 cup. Some meat release its water during cooking. Water needed for cooking remain same for different sizes of meat. What changes is the cooking time. Bigger sizes take more time to cook than smaller sizes.

Below mentioned information can be used as a reference guide to understand how much water to use to cook seafood and meat. It can be adjusted according ones judgement based on experience.

Meat and poultry:
Chicken 1 whole in pieces- 1 cup
Chicken whole(1.3 kg)- 1 cup
Duck -1 in pieces, turkey (breast, leg, thigh)- 1 cup
Lamb( shank, shoulder, stew meat)- 1 cup

Water requirement for cooking
Seafood:
Fillets(Cod, snapper, salmon, sole )- around 3/4 inch-1 inch-  3/4 cup of water
Steak( tuna, halibut, salmon)- 1 cup
Scallops- 3/4 cup

Please note that the above mentioned information is collated by personal experiences and by studying the manuals of hawkins pressure cooker. For more information on cooking time, cooking water, recipes, etc please refer to https://www.hawkinscookers.com/Cookbooks/AllIndianCookbook.pdf