int red_led=13;
int green_led=12;
int trigpin=2;
int echopin=3;
long duration;
int distance;
int length=400;
void setup()
{
  pinMode(13,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(trigpin,OUTPUT);
  pinMode(echopin,INPUT);
  Serial.begin(9600);
}
void loop()
{
  digitalWrite(trigpin,LOW);
  delay(200);
  digitalWrite(trigpin,HIGH);
  delay(100);
  digitalWrite(trigpin,LOW);
  duration=pulseIn(echopin,HIGH);
  distance=(duration*0.034)/2;
  if(distance<=(0.2*length))

  {
       digitalWrite(13,HIGH);
        digitalWrite(12,LOW);
      Serial.println("water level is less than 20%");
  }
  if(distance>=(0.9*length))
  {
    digitalWrite(12,HIGH);
     digitalWrite(13,LOW);
    Serial.println("water level is greater than 90%");
  }

}